Achaea

One of the more popular MUDs on the internet (which still makes it a shrimp compared to World of Warcraft), Achaea, Dreams of Divine Lands is an RP-enforced game that generates revenue via its pay-for-perks system. With enough money, you, too, are capable of trying to Bribe Your Way to Victory, only to discover it isn't that easy after all.

Achaea is notable for having a fairly complex combat system, and each of the various classes have completely different strategies for combat. It's also known for its aforementioned pay-for-perks system. In other words, if you want to become a strong combatant, expect to spend as much effort and possibly pay as much money as you did on your college education.

Before 2005 there was a guilds system in the game. To gain a class, you'd have to join the guild for that class, but it wouldn't stay permanent (you'd lose your class if you quit the guild or were kicked out) until you reached a high enough rank in the guild. In 2005 this was abolished in favor of "autoclass" which skipped the entire guild requirements and let someone join a class immediately. Depending on who you ask, this either destroyed the very core of the game, or was a vast improvement. An almost surefire way to start Internet Backdraft is to head to their forums and start a thread talking about how much autoclass rocks.

Iron Realms Entertainment, which makes Achaea, has three other games (Aetolia, Imperian, Lusternia), with the same game engine. They also all are pay-for-perks and have a fairly complicated political and combat system. Which means that if you spend a lot of money and/or time on one and decide to play another, all your hard work went down the drain and you have to start from scratch and do it all over again!

Not to be confused with 'Archaea'.

This game provides examples of:
 * An Adventurer Is You
 * Asskicking Equals Authority: In game, it's very common for players which are skilled at the incredibly complex combat system to be prime candidates for political positions. This is more marked in the more recent IRE games.
 * Bare-Fisted Monk: And of course All Monks Know Tekura and Kaido is essentially a derivative of Ki Attacks.
 * Body Horror: Transmogrifying into a Chaos Lord has some... cosmetic side effects.
 * Bribing Your Way to Victory: While you can enjoy the game and acquire anything in the game world without paying money for their virtual "credits," while you do so the rich kid will surpass you nigh-instantaneously, acquiring in days what it could take you years to gather.
 * Broken Base: Several things, but most infamously autoclass. Pre-Autoclass, you had to be a member of a Guild to use a given class, and if you didn't feel like adhering to that guild's rules, then you simply didn't play that class. Autoclass removed this limitation, removing the major form of player control over those classes.
 * Character Level: Higher level as usual means more health, but it also means a higher chance at critical hits. Once you reach level 80 you don't need to eat or sleep, and at level 99 you gain access to the Dragon race/class combination. Said dragons exist in a variety of many different colours, each with its own associated power.
 * Cloudcuckooland: Bopalopia. And you eat an oddly-colored mushroom to enter it.
 * Combos: Monks can use these.
 * Critical Hit: Your chance to do these and the multiplier they entail goes up with your level.
 * Dark Is Not Evil: There are distinct deities of Darkness, Chaos, Sin, and Oppression and Suffering (though the last two were once joined as Sartan and still hold sway over Mhaldor). Shallam and its Church, and sometimes Cyrene, perennially fail to distinguish between the adherents of these various paths and will do war on anyone they see as evil, much to the consternation of those who are, for instance Chaotic Neutral, Lawful Neutral, or even Lawful Good according to their native laws and chosen religion but do not follow the One True Faith. This has a tendency to make the rest of the world view them as Well Intentioned Extremists at best.
 * Death From Above: The name of an actual ability; you drop out of the treetops and attack someone on the ground level.
 * Druids: Comes in three flavours: the freewheeling Sentinel Class, the more mystical Sylvan class, and, well the Druid class.
 * Dual-Wielding: Special ability of knight classes.
 * Elemental Embodiment: Invoked in various flavours but most notably in the Viridian ability in Sylvan Elementalism, transforming the caster into something of an avatar of Nature.
 * Global Currency: Everything accepts either gold pieces or, in the case of artifacts, credits.
 * Go Mad From the Revelation: A powerful but tricky-to-use Occultist ability, Enlighten, essentially does this, with the effect that the enlightened character is unable to cure mental afflictions for a considerable period of time or until they die; due to how weakened they would be if this ability was successfully used on them, it's usually the latter that cures it. If you're playing and you see someone shout something about "No! It can't be true!", that usually means they just got Enlightened.
 * Grey and Gray Morality: Or maybe Black and Gray Morality, depending on how one sees Mhaldor's aims. Either way, a member of the "good" faction in the game is, at best, a Well-Intentioned Extremist. Even some of the more "neutral" characters within the setting seem to just want to be left alone and reap the benefits of the more strongly-aligned factions duking it out over the fate of the world.
 * Guide Dang It: Some of the quests; the fact the game administrators strongly discourage the sharing of quest information does not help. The most infamous is the Caer Witrin quest, which only a handful of people in the history of the game have ever completed.
 * Hollywood Voodoo: At least they give it the more exotic name of Vodun. Puppetry acts, more or less, the same way.
 * Item Crafting: The knight classes can, if they're skilled enough in the Forging skill and have the required materials, create weapons and armor for either themselves or to sell to others. It takes a while to make each one though, and the stats on each can be highly variable.
 * Also, Enchantment for Magi.
 * Runists also craft totems.
 * And let's not forget tailoring, jewellery, inkmilling, and cooking.
 * Land of One City: There are six adventurer-populated city-states (except Hashan doesn't exist).
 * Level Grinding
 * Mind Rape: There is an entire set of mental afflictions, and entire skillsets are centered around inflicting them. At the highest end of the scale, the Enlighten ability mentioned earlier on this list is full-fledged Mind Rape.
 * Money Spider
 * One-Hit Kill: Most classes have one or more of these, and they can get pretty nasty. Anyone who is good enough with a weapon can behead someone. Knights can disembowel their victims. Serpents can behead people by driving their whips through people's necks. Jesters can summon a jack-in-the-box that eats heads. Flinging the Death Tarot card at someone summons the Grim Reaper. Blademasters can slice people into bloody chunks with four well-placed slashes. Priests and Apostates can command their respective familiars to tear the soul out of someone. Apostates can also tear the heart out of their victims with their living dagger. Sylvans can plant a seed in someone that will grow inside them, eventually sprouting and shredding them from the inside out. Monks can kill using a backbreaker, but can also use their Ki Attacks to do one of two things: burn their victims to ashes or literally boil their blood. Voyria, a venom, causes spasms so great it breaks backs if it isn't cured in time. Shamans can shrink the heads of their victims while they are still attached. The prize for most gruesome, however, goes to the people who use Necromancy, and gain the ability to slice someone's chest completely open, rip apart as many of the poor soul's innards as possible, and finally drive a bone through their exposed heart.
 * Perpetually Static
 * Occasionally averted with global events such as the unification of Apollyon, God of Suffering, and Shaitain, God of Oppression as Sartan, God of Evil (and later splitting again), and the invasion of the Vertani, among other things.
 * Player Versus Player
 * Summon Magic: Several classes have skills that include summoning and controlling loyal entities, including:
 * Sentinels have the Woodlore skill which allows, among other things, the summoning various woodland creatures for assistance in combat.
 * Occultists can use Domination to reach the Chaos Plane to negotiate pacts with its denizens who can later be summoned to the prime material plane.
 * Mages and Sylvans have Elementalism which, unsurprisingly, includes four elemental creatures, though only two manifest as loyal entities, the other two activating instantaneous abilities.
 * Apostates can summon a Balzadeen in Apostasy, Priests a guardian angel with Devotion.
 * The knight classes get loyal falcons in the Chivalry skill, which must be acquired but are later treated like summon entities.
 * Sympathetic Magic: A key component of the Shaman skillset, Curses, Vodun, and Runelore, and once upon a time the Ritualism practiced by the Guild of Shamans as an immersive RP tool. Also invoked through Runelore with the Runewarden class and Puppetry in the Jester class.
 * Tarot Motifs: Done with the Tarot cards.
 * Warp Whistle
 * Welcome to Corneria: Though occasionally subverted if a game administrator takes control of an NPC to have conversations with players.
 * Wizard Needs Food Badly: You can starve to death... at least until you transcend such things by reaching level 80, at which point you have no need for food or sleep.
 * Words Can Break My Bones: The Occultist "truename" ability.