Game Breaker/Magic the Gathering



Being the first trading card game, Magic: The Gathering has a lot of Game Breakers. Part of this stems from the fact that the original editions of the game were little better than an Obvious Beta (so much so that the second release of the Limited First Edition was named "Limited Edition Beta" (With the first being "Limited Edition Alpha")); indeed, like most games that are played extensively, the lion's share of Game Breakers are discovered by players post-release. But the fact that Wizards of the Coast keep trying new things can't help. (Well, it does make the game more fun; we're just talking about the inevitable impact on game balance.)

The most famous of these are the Power Nine, from Limited Edition, which are banned in every format except Vintage, where they're restricted to one per deck:


 * Black Lotus is the Holy Grail of Magic cards; a genuine Black Lotus costs as much as a (well) used car these days, and with good reason; three mana of any colour you like for nothing is powerful. It's so powerful a card that does exactly one third of what Black Lotus does had to be banned. It's so powerful a version that requires you to throw your entire hand away in order to use it had to be banned. It's so powerful that even a version that requires you to wait three turns before you use it was a major component in a World Championship deck. Wizards have more or less given up on trying to release a "balanced" Black Lotus.
 * Mox Emerald, Mox Jet, Mox Pearl, Mox Ruby, and Mox Sapphire. These are just like basic lands, except they're artifacts; this means you can play more than one per turn.
 * More recently, Chrome Mox and Mox Diamond have kept up the family tradition by being restricted in Vintage, though this has since been reversed.
 * The Mox jewels and Black Lotus' infamy was honored and spoofed with the tournament-illegal Unhinged set's Mox Lotus.
 * A powerful, yet somewhat more balanced, tribute to the Mox jewels came in the Scars of Mirrodin set, in the form of the Mox Opal. Time will tell whether it joins its brethren on the banlist.
 * Timetwister may not seem very powerful, since it's symmetrical, but if it's the last card in your hand and your opponent's hand is full...you see where this is going. It's also the first card that conspired to make Lion's Eye Diamond useful.
 * Ancestral Recall. Part of a cycle of "boons" in which you pay one mana get three of something; the others were Giant Growth, Dark Ritual, Healing Salve and Lightning Bolt. Ancestral Recall was the only one to not be a common card, and the only one never reprinted. Drawing three cards for one mana is obscene.
 * Of the other boons, both Dark Ritual and Lightning Bolt have also been phased out, though the latter was given a (deliberate) comeback in 2010. Healing Salve has also been quietly left by the side of the road for being, in comparison, pretty lame. Only Giant Growth endured, being re-printed continuously until the 2012 Core Set. (Long story short: early editions of M:tG were just riddled with balance issues.)
 * Time Walk is the cheapest way to take an extra turn; at one point, every "take an extra turn" card was banned at tournament level due to the huge number of degenerate card combos involving multiple or infinite turns.
 * One of many, many combos with Time Walk was to put it at the bottom of your library with Soldevi Digger and then use Demonic Consultation to dig it back up. This cost your entire library, so required you to have everything in play you wanted in play, but by using the Digger each time Time Walk was cast you got to draw it at the start of the new turn, cast it for another turn, then use the Digger again...

But there are far more. Bear in mind notes regarding bans and restrictions; Wizards have more recently taken a far more liberal stance on these, and many cards that were once restricted or even banned entirely have had their rulings relaxed from their previous status. In addition, most card errata that radically change a card's function (eg those formerly in place for Great Whale and Time Vault) have been removed in favour of simply clarifying the rules actually on the card.


 * Probably the earliest broken combo in Magic was the combination of Channel and Fireball, which allowed a first-turn kill to anyone who could get hold of one mana more than it took to cast the two spells. Legend has it an early tournament caused the modern limit of four non-land cards; both players had 20 copies of Channel, 20 copies of Fireball, and 20 copies of Black Lotus, with the match being eventually decided by one player failing to kill his opponent on the first turn. Channel was banned for a very long time, until it became clear the game had changed so much that paying 19 life to power a single easily-countered Sorcery was tantamount to suicide; as a testament to its ability to be used for terrible things, it remains restricted to one copy per deck even in formats where it's legal.
 * This one was so well-known it was featured in a comic in the official magazine The Duelist.
 * Perhaps the most powerful card-drawing card ever printed is Contract From Below. This references an old mechanic called "ante" where players set aside cards at the start of the game and the winner took them at the end, which was axed after falling foul of anti-gambling laws in some US states. The Contract is a ridiculous card; sure, you ante up an additional card and discard your hand (the latter of which could be beneficial in the right deck), but you get 7 cards for only one mana. Like all ante cards, it's illegal in all formats; even if this wasn't so, it's staggeringly overpowered and would likely still be banned.
 * The first combo deck in the modern sense was called "Prosbloom," after the two cards that comprised it, Prosperity and Cadaverous Bloom. Rather than relying on creature combat, this deck was based around the "engine" created by these two cards; cards were discarded for mana from Cadaverous Bloom, which then fuelled a Prosperity; this pulled in more cards for the Bloom, with the eventual goal of creating a mega Drain Life for the killing blow. This totally altered the way the game was played.
 * Cadaverous Bloom also combos with Oath of Lim-Dûl in an earlier version of the various cycling exploits possible with Fluctuator. Don't like a card? Who cares, sling it out with the Bloom then pay the Oath to draw another.
 * Time Vault has been broken so many times and in so many ways that at one point the Gatherer text used to be a total rewrite of the card which made the ability put a counter on Time Vault which could only be removed by skipping a turn, so that untapping it didn't allow it to be used. The classic method of cheating around the "skip a turn to get a turn" mechanic was Twiddle, but the really evil combo was Animate Artifact / Instill Energy. This allowed Time Vault to be used again each time it created a turn and so made it so the other player could never take a turn at all, and this combo made it the first non-ante card to be banned at tournament level. These days you can do that with a single card, Voltaic Key.
 * Another combo was with the otherwise harmless-looking Flame Fusillade. Since at one point Time Vault's errata text allowed it to untap at any time, this was an easy infinite damage combo.
 * Another early combo was based around the long-forgotten Kird Ape, and actually got three of the four cards in it banned or restricted for a very long time. The idea was to cast a Kird Ape with a forest in play (for a 2/3 creature), then give it Giant Growth for a 5/6, then use Berserk to make it 10/6, then Fork the Berserk to get a 20/6 game-winner for just 4 mana. Kird Ape was restricted in Legacy for a while, while Fork and Berserk were both on Vintage's restricted list.
 * "Tutor" is a name for a series of cards, but also a more general name for any card which has the ability to draw a specific card from your library. The ability is often gamebreaking, since there are some very powerful cards you can go looking for. The original is Demonic Tutor.
 * Not only is Demonic Tutor uncommon, but also many designers are itching to straight reprint it (they have printed it in promo sets such as the Duel Decks series (Garruk vs. Liliana)); however, two mana for any card in a deck has constantly been too powerful. The best we can get for now is an otherwise identical card that costs twice as much.
 * Vampiric Tutor, which appeared in Visions, is arguably more broken. While it causes you to lose two life and puts the card on the top of your deck rather than directly in your hand, it also costs only one mana to cast and comes at instant speed. And like Demonic Tutor, it's spent some time on the banned/restricted list.
 * Even Demonic Tutor's terrible offspring Grim Tutor can be found enabling degenerate combo decks in Legacy and Vintage. Seeing as it's really the best option that isn't banned or restricted, it's really a player's only choice if they just gotta do something broken.
 * In Legacy Infernal Tutor and Lion's Eye Diamond do a reasonable impression of Demonic Tutor and Black Lotus in combo decks. Unsurprisingly, they (especially Lion's Eye Diamond) tend to be the poster children of degenerate combo in Legacy. Also, the reason why Legacy players can't have nice things (at least if your definition of nice things is blue not being the de facto best color and/or banning Force of Will).
 * Lion's Eye Diamond hasn't really gotten its fair share of space here, relative to how broken it is. Lion's Eye Diamond (LED) is the boogieman that hides under non-blue Legacy decks' beds. It enables pretty much every turn 1 or 2 kill in Legacy. Most recent Dredge lists rock LED alongside Black Lotus but some play LED over Black Lotus. While it's quite possible this is simply a budget concern, the simple fact that it's even a little questionable whether LED is better than the most powerful spell ever printed, if only in this one deck, speaks volumes about its power level. It even managed to be voted the 65th best card in Vintage in a poll of some well known Vintage players on Star City Games, despite it failing to make a showing in any deck except Dredge for at least a year (outside of the corner case Belcher deck). If nothing else, LED emulates Black Lotus closely enough that it will likely never be safe to unrestrict it; even if it stops showing up in any decks. Wizards will likely never make a 'fixed' Black Lotus that is this good again and LED will be safe and secure in spot as one of the top 2 'fixed' Black Lotuses along with Lotus Petal.
 * Balance. In theory, this card balances out the playing field. In practice, it's Armageddon, Wrath of God and Mind Twist, all in one card. The trick to it is to ensure you have Artifact mana and damage sources (with the classic being multiple copies of The Rack), while your opponent does not; they're suddenly left with one card in hand and one land to cast it with. During "Necro-Summer," it was noted to be one of the only cards that the Necropotence decks had any trouble with, since with Balance they'd suddenly find their discard and land destruction had been playing right into their opponent's hands, while they had to throw away all the cards they'd paid for, leaving them with only painfully low life to show for it. A later ally to Balance decks was Zuran Orb, allowing the White player a clean way to throw away all his lands for profit before slapping Balance on the table.
 * The secret to Balance's power is simple: it controls the number of lands, creatures, and cards in hand, but has no effect on the number of artifacts or enchantments, so while it may clear the field of creatures, reduce the number of lands, and cause an opponent to lose their hand, if you have a large number of artifacts on the field that can deal damage, you win, since by the time your opponent can recover (barring an insanely lucky draw), it's game over. And all for two mana.
 * And, since it's been mentioned, Mind Twist itself. An obscenely undercosted discard spell, it was so loathed that it won a player poll of cards to be excluded from Fifth Edition by a substantial margin. It proved particularly unpleasant when pulled out early in the game using Dark Rituals and combined with one or more copies of The Rack. It was the third card to be banned outright in all tournaments for being overpowered (Time Vault and Channel being the first two), and the first to be banned entirely for what it could do by itself, rather than any combos including the card.
 * Fastbond. Remember why Moxen are good? This lets you play as many Lands as you can draw. Everything is now a Mox, all for one mana and a paltry single point of damage each. The combo that got Fastbond banned was with Storm Cauldron, which essentially turned Fastbond into Channel for coloured mana.
 * Not to mention its interaction with Gush, letting the Gushbond player generate mana and draw cards at the small cost of 2 life. Actually, Gush itself is a ridiculously broken card. It's been on and off the restricted list in Vintage multiple times (it's currently legal and unsurprisingly Gush based blue decks are Tier 1) and it's been banned in Legacy since the banned lists were split. Oh yeah, Fastbond isn't even legal in Legacy; Gush is banned purely on its own merits.
 * It gets worse. Using Fastbond's ability to play more than one land lets you also play Glacial Chasm which reduces all damage to zero. Infinite mana, anyone? And the real kicker is that even if your opponent is cradling a Fork in his hand, that 37 billion damage fireball you unleash on him still does zero to you when he duplicates your one card nuke.
 * Sol Ring, sometimes called the tenth member of the power nine, is another card from the days before they learned the folly of providing cheap cards that provided more mana than they actually cost, especially repeatable ones.
 * High Tide is a one-sided blue Mana Flare for just one mana. It's often combined with untapping effects to generate obscene amounts of mana. The classic is Palinchron; with the Islands now tapping for 14 blue mana instead of 7, it's easy to bounce the Palinchron in and out of play as many times as you want to, netting 3 blue Mana each time. Mike Flores described the original Extended High Tide deck as "the most hated deck in the history of tournament Magic, the poster child for Combo Winter."
 * After dominating Extended for a while High Tide decided it wanted to become the best combo deck in another format so it showed up in Legacy as Solidarity, a deck that ran on the same concepts but played only instants. Solidarity's time came and went and High Tide never really caught on in Vintage so Wizards give Legacy High Tide its most powerful weapon: Time Spiral. After a brief period of panic Mental Misstep stepped in and neutered it again. Then Misstep got banned and now Legacy players can only take solace in the fact that the most powerful mana generator in the deck (Candelabra of Tawnos) is restrictively rare and expensive (the Director of Sales at Star City Games estimated that there are less than 250 playsets of Candelabra in circulation; that's a very, very small number considering every good High Tide deck wants a full playset).
 * Dual lands, which have almost no disadvantage save forlandwalk. Wow, color doesn't exist anymore.
 * Interestingly, not all of these cards are equally banned.
 * Another classic unbalanced land is Strip Mine, which is restricted in Vintage and banned almost everywhere else. Land destruction should be a little harder to come by than having a mana-producing non-Legendary Land on the table. Library of Alexandria is a similar case of two abilities that have no business both being on a Land.
 * And on the theme of unbalanced Lands, The Tabernacle at Pendrell Vale is a horribly nasty card to drop on any "weenie" deck built around cheap creatures. It gets even more unpleasant when combined with something like Living Plane, since this means most Lands are rendered useless by having to pay their own upkeep cost with the mana they produce. Mana Web is another nasty combo.
 * Black Vise was one of the earliest restricted cards; back in early Magic before the proliferation of one- and two-mana drops, if one of these came out on the first turn you'd consider yourself lucky to get away with six damage; with multiple Black Vises in play, you could easily be almost out of the game before it had really even started. Players would often have four on board just to give them a quick cast to get out from under an opponent's Vise. Restricting it, however, allowed other broken cards it had been keeping in check to come out.
 * One such card was its opposite, Ivory Tower. This became a staple of Necropotence decks, granting them life to draw more cards from the cards they'd paid life to draw.
 * Necropotence itself seemed useless until the restricting of Black Vise which had previously made it unplayable; in addition, the attitude that life was, well, life, rather than a resource, had been prevalent. When players realised that paying life to draw cards wasn't so bad when the same colour had things like Drain Life to get it back and kill their opponent at the same time, it was suddenly everywhere, leading to a period nicknamed "Necro-Summer" where almost every deck in tournament play was a Necrodeck or a deck specifically designed to beat "The Skull." It didn't help at all that under the old rules a player didn't die until the end of the phase even if their life dropped below zero, meaning Necro players could literally kill themselves digging up Drain Life and still finish with a positive life total, or simply use Mirror Universe to give their life total to their opponent. Attempts to depower the deck included bans of Dark Ritual and Drain Life, along with restricting popular Life sources Zuran Orb and Ivory Tower. Ultimately, the card itself was banned; since then it's been unbanned, perhaps most infamously being used to power Yawgmoth's Will / Dark Ritual decks during Combo Winter. A mighty card-drawing engine, Necropotence continues to turn up when a deck is designed around digging up the pieces of a combo quickly, and is still restricted to one copy per deck in tournaments.
 * Necro also powered the earlier versions of the Trix deck, which was based on using Donate to give an opponent Illusions of Grandeur, something combo players had been searching for a way to do more or less since Illusions came out.
 * It's sometimes said the only reason turbo-mana instant Dark Ritual seemed fair was because it's always been around; it's powered numerous superfast combo decks over the years, and was once banned during the attempts to cripple Necropotence decks.
 * Dark Rit was also thematically inappropriate; as the Color Pie was re-defined, the decision was made to limit fast mana generation to Red.
 * White had its own turn at being broken, with the combination of Winter Orb, Icy Manipulator and Armageddon allowing them to shut down the entire game and win by default when their opponent ran out of cards. Such "prison decks" lost some degree of potency when the rules for Artifacts were changed (under the old rules, an Artifact's effect was "turned off" when it was tapped, meaning Winter Orb only affected the owner when they wanted it to), and largely disappeared with the advent of fast combo decks that won long before the board could be locked down, being replaced by much quicker "control" decks. Rising Waters is a more modern variant of Winter Orb.
 * Stasis is a classic lock deck card, limiting the amount of mana available by preventing lands from untapping. The traditional combo was with Kismet, making sure that players couldn't break the lock by playing new cards either; typically, the kill card was Serra Angel. This evolved into Chrono-Stasis, using Chronatog at the end of an opponent's turn to skip the player's own turn, thus dodging the upkeep cost of Stasis while the opponent slowly ran out of cards.
 * Zuran Orb is an extremely powerful card for any deck which needs life more than it needs Lands; Balance decks and Necrodecks love it equally, and it's especially powerful when combined with Fastbond.
 * Land Tax. Combine with an Armageddon and don't play any lands that turn for extra fun. Land Tax also has combos with cards that like you to have drawn a lot of cards or have a lot of cards; classics include making sure you always draw a card with Library of Alexandria and stacking up extra draws for Sylvian Library swaps.
 * Shahrazad was banned more or less on the basis that players would use it to force games to go to time in tournaments [by playing it multiple times until everyone involved lost the will to live] and therefore ensure a draw. Similarly, Chaos Orb and Falling Star were banned because judges were bored of having to make time-wasting rulings about which cards they landed on or how high they were flipped, and because they forced players to space their cards in a manner that made actually playing the game awkward.
 * A famous urban legend amongst players was that one man won a tournament by actually tearing up his Chaos Orb and sprinkling the resulting confetti over the table. This incident became immortalised in the Unhinged card Chaos Confetti.
 * Another version has his opponent win because his deck was now one card short.
 * Nevinyrral's Disk was a popular choice for dealing with anything big and bad; the card literally destroyed everything in play for five mana and a turn's wait; this made trying to differentiate the "colours" a largely futile exercise, since everyone could kill everything; it was duly banned, though today is not even restricted.
 * Phyrexian Dreadnought is quite popular with people trying to do nasty things; an almighty 12/12 trampler that costs just one mana, for a (supposedly) major pay-off of requiring the player to already have creatures as or more powerful in play. However, combo players instead looked for ways to get it to do things before having to sacrifice anything (and found Pandemonium), or sneak it into the game without the effect ever triggering (and found Illusionary Mask). An Obvious Rule Patch was thrown out in an attempt to counter the first saying that the sacrifices had to be made or the Dreadnought would never "come into play" to trigger Pandemonium, but the errata was later removed. A modern way to abuse the Dreadnought is to Stifle the comes-into-play effect, giving you a 12/12 trampler as early as turn 2 with no drawback whatsoever.
 * It is quite easy to do this on turn one with any of the moxen, simian spirit guide, elvish spirit guide, lotus petal, black lotus, or even Tolarian Academy with a couple free artifacts. With the right draw, it would technically be possible to put 2 into play on the first turn.
 * The Rath and Urza cycles had a huge number of these. The Urza Block has the distinction of having had more cards from it banned in tournaments than any other. It was said at the time that the game had three phases: draw 7 cards, look at your cards, win the game. There's a reason it was called "Combo Winter." It should also be noted that Urza's Saga was the only set to get the entire design team for the set called up to the head office and yelled at.
 * Memory Jar was unique in being banned before it became tournament-legal; though it's an enormously depowered version of Contract From Below, drawing a new hand is still far, far too powerful an ability to have floating around in an environment full of other power cards.
 * What makes Memory Jar broken is that it's an artifact so it can be cast off be Mishra's Workshop, played in any deck and most importantly Tinkered for (just in case you couldn't draw any of your other 3 mana draw sevens). Actually Time Reversal has the same casting cost as Memory Jar but is utter trash simply because it is not an artifact.
 * The above-mentioned Yawgmoth's Will is one of the most powerful cards ever printed: just get a lot of cards into your graveyard (something Black is good at), especially multiple copies of Dark Ritual, then drop the Will and you suddenly have obscene card advantage, usually enough to win the game outright. Restricting it, uniquely, doesn't really help, since it's rare a player will want to draw it early on before they've had a chance to fill up their graveyard. A particularly nasty Vintage deck called Long.Dec (scroll down) used Burning Wish to abuse a sideboarded copy; with a 60% first-turn kill rate, it was one of the most powerful decks in the format's history and duly got Burning Wish (and Lion's Eye Diamond, a card once thought completely useless) a place on the Restricted list alongside Yawgmoth's Will itself.
 * Yawgie got another broken card to his name, in the form of Yawgmoth's Bargain. This is turbo Necropotence, skipping that whole annoying part where you have to actually wait to get the cards. On the one hand, it's expensive. On the other hand, it's in the same block as Skirge Familiar. This did not end well; in fact, the Bargain was banned in the Extended format before it had even rotated into it.
 * There's a common joke that Yawgmoth's Bargain is "I'll take your common, useless Healing Salve and give you an out-of-print, rare, Vintage-restricted, game-breaking Ancestral Recall." Far worse was that the Ineffable combo'd with "spellshaper" cards in the next block, meaning you essentially had "Pay 1 life: Do whatever the hell you want."
 * Mark Rosewater has referenced Yawgmoth's Bargain a couple times when talking about mistakes he made in card design and this taught him that that anything that will exchange 1 card for 1 life and is reasonably costed is going to be broken. Interestingly, in another article he implied that they justified the card by reasoning that 6 mana was too expensive for it to be broken (in all fairness, six mana is a lot; the only other card that costs more than 4, isn't cheated into play, and is still played in Vintage is Mind's Desire which is so broken it shares the distinction alongside Memory Jar of being one of 2 cards every to be banned/restricted before seeing major tournament play). Which begs the question: is there ANY mana cost that would make this effect fair?
 * One of the best lands ever printed, Tolarian Academy. It's known for being the centerpiece to dozens of broken decks and infinite mana combos, including:
 * The Grim Monolith / Tolarian Academy / Voltaic Key combo.
 * The Tolarian Academy / Candelabra of Tawnos / Capsize combo. This is a little harder to see since the main rule isn't actually on Candelabra of Tawnos. Old Artifacts were always assumed to tap to use their abilities. With at least nine Artifacts in play, you tap the Academy for nine blue mana, use the Candelabra to untap the Academy (cost 1), then use Capsize (with Buyback, cost 6) to return the Candelabra to your hand, casting it again afterwards (cost 1). The board is now back to how it was, except you have one blue mana. Repeat until you have more mana than you know what to do with.
 * Somewhat similar to Tolarian Academy, Gaea's Cradle. Now, remember there are lands that are creatures, mana source creatures, cards that make lots of token creatures, and Living Lands. So, this can work out as a zero-cost, one-way Mana Flare which also turns every creature into a Forest you don't need to tap.
 * Grim Monolith itself is also broken when combined with Power Artifact, allowing it to untap for one less mana than is generated by tapping it.
 * Dream Halls is a powerful card which allows any coloured card to be played by simply discarding another. It was at it's most powerful when played with 'free' creatures like Great Whale; you could throw down a Great Whale and untap all your Lands, even though you hadn't actually tapped any lands to pay for it. Errata were issued quickly saying that such creatures could only untap lands if they came into play from your hand, though these have since been removed.
 * Tinker. Combined tutoring with automatic casting, all for three mana and sacrificing an artifact. Since artifacts exist that cost nothing, as long as it was around it was impossible to balance any artifact with a high casting cost; all artifacts could be cast for three mana.
 * Not to mention that Mirrodin Besieged "blessed" us with Blightsteel Colossus so now blue mages can win in one swing instead of two or, God forbid, three like the old, crappy robots of yore.
 * Recurring Nightmare, a repeatable way to put creatures from your graveyard into play, thanks to having zero-cost automatic buyback. Combos with, among others things, Great Whale; endlessly Recurring a pair of Great Whales (one in the graveyard and one in play, constantly swapping which is which) creates an infinite mana loop. The killing blow from this deck was to shift Recurring Nightmare to a graveyarded Triskelion, which was then Recurred until it had shot the other player to death; if you have it deal the last hit to itself, Triskelion has the advantage of killing itself, allowing it to return anew.
 * Survival of the Fittest is a reusable, super cheap tutor which practically makes it broken by default. Once upon a time Vintage players feared a deck called German Tools 'N Tubbies or simply TNT that used Survival alongside Mishra's Workshop to do lots of broken things. The deck would get Anger, Genesis, and Squee, Goblin Nabob into its graveyard in order to tutor up a hasty Goblin Welder who would procede to cheat Juggernauts into play (they were the Tubbies; Juggernauts were credible threats back in the day, surprisingly). Also, it played singleton creatures who did something specialized to help them swing matchups that otherwise might be not so hot.
 * Oath of Druids is another "balancing" card, and another one that turned out to be hideously broken if a deck was built around it. Continuing the Balance tradition of being ridiculously cheap, it ruled tournaments in various forms for a long time prior to being variously banned and restricted; an Oath deck simply plays control while it digs up the Oath, then goes off almost instantly. A classic combination was for players to use Forbidden Orchard to give their opponent creatures, allowing them to bust out huge creatures from their own deck as early as turn 2. These days it's potentially even more powerful, since the Oath works out as paying 2 mana for huge creatures like Emrakul, the Aeons Torn.
 * Oath also continues the proud tradition of Ancestral Recall: namely, ridiculous power disparity within cycles. Oath of Druids was part of a cycle of Enchantments in Exodus that provided a each player a benefit during their upkeep provided they have less of a specific resource than their opponent. The rest range from unplayable trash to I might have seen it in Block Constructed. Here's the rest of the cycle: Oath of Ghouls (black), Oath of Lieges (white), Oath of Mages (red) and Oath of Scholars (blue).
 * Cursed Scroll looks like a bluffing card, until you start emptying your hand before using it. When your opponent can only choose the one card you drew that turn, it works out as a colourless Shock. For a while, you could reasonably expect to see four of these in every top-level deck which didn't like holding cards.
 * Lotus Petal does exactly one third of what Black Lotus does, and still proved too powerful. Zvi Mowshowitz once defined a broken combo deck as one that would use Lotus Petal if it could.
 * And Stronghold got in on the act with a Mox, Mox Diamond. While not as powerful as its brothers in the Power Nine, it's still spent time on the restricted list.
 * Intuition is much like Kamigawa's Gifts Ungiven, save that you only get one card; however, it has the huge advantage that you can search for three copies of the same card with it and give your opponent no choice at all as to what you end up getting. It's also powerful in reanimation decks, since it can be used to make your opponent put big creatures into your graveyard.
 * Hermit Druid was killed off by bannings almost as soon as decks using it appeared; the general idea of "Angry Druid" decks was to have few or no basic lands, allowing the Druid to dump the entire library, filled with powerful creatures, into the graveyard. A reanimation spell would then be pulled back into the library with Krosan Reclaimation and used to pull Sutured Ghoul from the graveyard (usually picking up Dragon Breath along the way); the resulting trampling mega-Ghoul, typically powered by multiple Krosan Cloudscrapers, would generally easily win the game.
 * Masticore, an efficient creature that regenerates and most importantly gives your deck the ability to burn down creatures no matter what color you're playing.
 * In its heyday, it was played heavily in blue control decks as a finisher. At the time, blue control was referred to as "Draw-Go" because that's how its turns went - "I draw. Go." It had a ton of cards laying around to pitch to Masticore once it hit the table. And it could easily burn out a lot of the creatures that blue let through to the table early on in the game. When blue is doing most of the burning in your format, something's gone horribly wrong.
 * Windfall, similar to Timetwister in its ability to refill your hand while giving your opponent nothing.
 * Fluctuator. Cycling is a mechanic which allows you to discard a card in your hand to draw a new one, by paying the cycling cost. All cycling costs at the time were the same as the amount this card reduces them by. In other words, if you don't like your hand, just throw out cards and draw more until you do, all for nothing.
 * Time Spiral was broken for pretty much the same reasons as the original Timetwister. Of course, it's more expensive. But came out in the same format as Tolarian Academy. Oh, and because Tolarian Academy can be among the lands you untap, you can quite easily gain mana by casting it.
 * Mind Over Matter, one of the most versatile combo enablers in magic. Among many many others, see Tolarian Academy. Again.
 * Sapphire Medallion. Because blue has such problems getting hold of mana in the Urza Block they needed a special card to make all their spells cheaper. Presumably the card letting you set your opponent's deck on fire wasn't powerful enough.
 * Metalworker, a hideously undercosted creature that dovetailed right into the "have loads of artifacts" Tolarian Academy decks to give them even more fast mana. These days it can produce infinite mana when combined with Voltaic Construct; all you need to do is have more then one Artifact in your hand.
 * Morphling, because creatures that can't do absolutely everything are so dull. Any two of its abilities would make it undercosted; with all five, there's little wonder how it earned the nickname "Superman."
 * If it's just big creatures you want, then Tinker for a Phyrexian Processor. The ability to put Minions into play for 4 mana no matter how big they are is powerful in itself, nevermind all the ways to make it activate more cheaply or use it multiple times in a single turn.
 * Replenish auto-casts every Enchantment in your graveyard for 4 mana. Bear in mind that Academy Rector costs the same, only gets one Enchantment into play, and has to die first, and is regarded as one of White's best cards. The Replenish deck would sit back loading the Graveyard with Enchantments using Attunement, then throw out expensive, powerful Enchantments like Parallax Wave, Opalescence and Seal of Clensing all at the same time. It was duly banned or restricted in every format.
 * Humility. There are cards that hose colours, cards that hose types, but only one hoses "creatures that do anything" to this scale. To add to the fun, if you can turn your opponent's lands into creatures they can't tap for mana anymore. Play it with Opalescence in play to make your opponent's head explode as they try in vain to figure out how the two cards interact with each other (just look at the errata on Humility - hey, you just lost D6 SAN and gained ten Cthulhu mythos. Congrats!). Depending on the order of casting, day of the week, phase of the moon and whether your human sacrifices have pleased benevolent Yawgmoth, Humility can actually end up removing it's own effect and becoming a 4/4 creature.
 * Stroke of Genius is one of the most powerful card-drawing cards, to the point at one Pro Tour a player in a tournament match resigned after asking to read the card text. It was typically the killing card of any Urza-block blue deck; making the other player draw 54 cards being auto-lose. This was often preceded by the player using it to dig out most of their own library, a procedure perhaps inevitably called "stroking yourself."
 * Worldgorger Dragon ended up banned in several formats due to the way it interacted with enchantments like Necromancy, Animate Dead and Dance of the Dead. The general idea was to get the Dragon into a graveyard, then get it back into play with one of these enchantments; the Dragon would remove the Enchantment that bought it to life from the game as it came into play, killing itself and bringing back all your other permanents...untapped. Along with them, the enchantment would return, ready to target the Dragon again, and in response you tap the lands for mana. This could be repeated indefinitely, and would result in a draw unless it could be interrupted somehow. The simplest win condition for such decks was to channel the mana into a massive instant-speed spell like Ghitu Fire or Stroke of Genius, but later versions would graveyard a card like Ambassador Laquatus, Shivan Hellkite or Sliver Queen with an infinitely repeatable ability, then have the enchantment target it instead of the Dragon to break the loop. A third version was to use cards with powerful comes-into-play effects which triggered every time the cycle ran; one variant used Eternal Witness to endlessly recycle and use Ancestral Recall on the other player until they ran out of cards.
 * The interaction between Dragon and Animate Dead is also notorious for being one heck of a rules headache. Even though Dragon is no longer the dominant force it once was (although it still shows up and places from time to time) it's been suggested (although not proven) that it remains of the Legacy banned list because of the rules problems it creates. The combo has been called a "rules glitch" and when it was commonly played judges noted that they got inordinate amounts of rules questions regarding interactions with the combo. In addition, players tend to dislike playing against the deck because without a Bazaar of Baghdad in play or a win condition in hand or the graveyard casting a reanimate enchantment on Dragon ends the game in a draw because there is no way to break the loop. This is a common tactic employed by Dragon players in the face of defeat (Necromany even let them do at instant speed so they could respond to lethal damage by forcing a draw) and so it was not too uncommon to see matches with Dragon decks go to 4, 5 or more rounds.
 * Mind's Desire was restricted in Vintage before it was even tournament-legal, owing to the huge number of disgustingly powerful things that can be done with as many free spells as you've played spells this turn; the typical play was to use Mind's Desire to build up the storm count further for a lethal Tendrils of Agony.
 * While the Kamigawa block was otherwise fairly low-powered, it did have Gifts Ungiven. This extremely powerful tutor card essentially made your opponent pick how they were going to die; it's restricted in Vintage and banned in several other formats.
 * There was also Umezawa's Jitte. Not quite as game-breaking as the likes of Skullclamp, but severely undercosted for its powerful abilities.
 * There's also the Mirrodin block, a very Artifact-heavy block with the ability to even have Artifact lands, the only cards that traditionally couldn't be Artifacts. So, your entire deck can consist of Artifacts (though this required some thought as the artifact lands were limited by the 4 of a kind rule). Setting aside the Affinity mechanic (cards that get cheaper the more of a certain type of card you have, and why yes there were cards with 'Affinity for Artifacts'), let's throw in Arcbound Ravager that gets tougher every time you get rid of an Artifact. Hell, while we're at it let's throw in Disciple of the Vault who deals a point of hard-to-redirect life loss (not damage) to your opponent every time Arcbound Ravager gets tougher. Now, let's remember you can have up to four Disciples in play at once; this means the 55 cards in your deck that aren't Disciples or the Ravager can kill your opponent eleven times over and give you a 56/56 creature, and if that somehow dies it allows you to make any other artifact creature in play a 57/57 creature and your opponent loses four life just for doing that. As if that wasn't enough, you could also give the Ravager Cranial Plating so that any Artifacts you hadn't sacrificed to it (including the Cranial Plating and the Ravager itself) also made it tougher. The Artifact Lands, Arcbound Ravager, and Disciple of the Vault all ended up banned. Mirrodin also gave Vintage players the extremely nasty Trinisphere.
 * Seemingly trying to cement Mirrodin as the next Urza / Rath block in power terms, there was also fast mana in the form of Chrome Mox, which had a visit to the restricted list in Vintage in 2004.
 * Skullclamp. What's the problem that Zerg Rush decks often face? They run out of cards, and if that's not enough to kill their opponent they lose momentum. So they printed an extremely cheap equipment that lets you strengthen or kill your creatures and draw two cards every time it happens.This article explains that it was banned because it was sucking the entire format into a Skullclamp "black hole."
 * Æther Vial also saw a trip to the banlist; since it puts cards directly into play without requiring them to be cast, they can't be countered. Free, uncounterable creatures every turn proved irresistible to a great many decks.
 * Some Eternal deck archetypes are built on quirky instawin combos; Painter / Grindstone comes to mind as one of the more prolific in recent years, mainly due to the satisfaction of milling someone's entire deck in one go. These cards are rarely banned on the grounds that getting the cards out is the real challenge of combo decks.
 * Another popular instawin combo has been broadly termed "Hulk Flash," which worked by comboing Protean Hulk and Flash to assemble a suite of game-winning creatures. Some variants of the deck could win on the opponent's upkeep of the first turn when going second.]]
 * Dark Depths is one of those cards that combo players study intently to figure out how they can make them go off quickly, and for a long time they couldn't. But sure enough, with Urborg, Tomb of Yawgmoth to make Dark Depths produce mana and Vampire Hexmage to yank the counters off it, it's possible to have a 20/20 creature in play as early as turn 1 (using Fastbond), and turn 2 otherwise.
 * Let's not forget the Unglued and Unhinged Self-Parody sets. All cards from these sets are banned in normal play, but some of the cards from these sets are so overpowered that if used in normal play they would be considered an enormous game breaker. R&D's Secret Lair (which doesn't so much break the game as destroy it) and Gleemax (Which lets you control any card in play if you can sneak around its enormous casting cost) are key examples.
 * Jace, the Mind Sculptor has the distinction of being the first of the new planeswalker card type to be banned, and while still in Standard too, the format which is both the most heavily scrutinized for card interactions and the one in which they are most reluctant to ban cards. In April, one tournament saw every top 8 finisher running the maximum 4 copies of Jace, The Mind Sculptor. There were 32 copies of Jace and 32 copies of Preordain in the top 8 - something almost unheard of in Magic history. At the time of the ban Jace was selling for between $80 and $100, a shocking cost for such a recently printed card.
 * From the same set as Jace, Stoneforge Mystic, a card that allows you to fetch any Equipment, then later put it into play for two mana rather than what it actually costs. It was "merely" good for awhile, but then a card called Sword of Feast and Famine came along to make it awesome, especially in combination with man lands and Squadron Hawk, all of which have evasion, making repeated equips more bearable. Then a card called Batterskull was released in the New Phyrexia set, giving the Stoneforge Mystic an even better equipment to put on the table (essentially casting an uncounterable 4/4 creature with vigilance and lifelink for 2 mana as early as the third turn). This was also banned at the same time as Jace, the article explaining why commenting that the two were dominating tournament play to a degree possibly unprecedented in Magic history.
 * There have always been a lot of possible infinite combos in the game.
 * They tried again to make a "balanced" Black Lotus with Lotus Vale at the cost of two untapped lands to be sacrificed to the graveyard. Nice and all, but when you combine it with the aforementioned Fastbond and Land Tax and for giggles, play Crucible of Worlds and Darksteel Garrison and you're not going to run out of any lands pretty soon. Oh and all of these are legal (except for Fastbond and Land Tax) in Standard.
 * The real error was that Lotus Vale could originally be tapped in response to having to sacrifice it for not paying the cost. Consequently Oracle had to completely rewrite the wording.
 * From the Avacyn Restored set, there's Exquisite Blood. Doesn't seem too bad, does it? Now combine it with Sanguine Bond. Anything that triggers the ability of one will cause the second one to trigger, which will cause the first to trigger again, which will cause the second to trigger again, and so on, giving you an infinite loop that lets you kill all your opponents and steal their life as soon as either you gain life or anyone but you loses life.
 * Innistrad gave us Mindshrieker, which may just take over from Morphling as Blue's invincible killer of choice. Day Nine has stories about how this card ruined his day.