Apprentice Adept

The Apprentice Adept series is a seven-book fantasy and science fiction series by Piers Anthony. The series takes place on two worlds occupying the same space in two different dimensional planes: Phaze - a Magical Land in Medieval Stasis and more or less ruled by the Adepts, the strongest magic users, each specializing in a separate aspect, and Proton, a barren mining planet of high technology, ruled by the Plutocratic Citizens (who control the immense wealth of the Protonite mines). The worlds are divided by The Curtain, an energy field only visible to those capable of crossing it (someone without a doppelganger on the other side).

The first trilogy (Split Infinity, Blue Adept, and Juxtaposition) starred Stile, a Proton serf who, after a mysterious assassination attempt destroyed his career as a race jockey, becomes the central figure in an ancient prophecy to Save Both Worlds from destruction, or ensure said destruction.

The second trilogy (Out of Phaze, Robot Adept, and Unicorn Point) featured Bane and Mach, the sons of Stile and Stile's opposite number, Blue, and their efforts to keep the previous impending doom from happening all over again.

The seventh and final book, Phaze Doubt sees the newly-merged worlds dealing with an alien invasion, and the Batman Gambit meant to deal with it and prevent future ones.

This series contains examples of:

 * AI Is a Crapshoot: In this case,
 * All of the Other Reindeer: the unicorn Neysa is an outcast because of her small size and horse-normal coloration.
 * All Your Powers Combined: Anyone with the Book Of Magic gains the ability to use every school of Phaze magic.
 * Alternate Universe: Phaze to Photon, and vice versa. Not quite a Mirror Universe (because morality isn't reversed), but it otherwise fits the trope: people born on Proton have a counterpart in Phaze that is as close to identical to them as possible while still being consistent with the setting change. In particular, magical power in Phase translates as wealth and Game-skill in Proton.
 * Anguished Declaration of Love: Mach makes one towards Fleta at the end of Out Of Phaze, via the the "Triple Thee". Its powerful enough to break the enchantment she'd put on herself to commit suicide.
 * Badass Normal: Stile, at least in Proton.
 * Batman Gambit: used Red's Adept paranoia against her in order to make sure  at the right time.
 * Best Her to Bed Her: Brown (though it's only a crush), Merle, Neysa, Tania
 * Blessed with Suck: Al - a half-vampire who's allergic to blood.
 * Bizarre Alien Biology: The Amoebans are gelatinous masses who eat through their skin in their normal forms. They also have Voluntary Shapeshifting abilities which they can use to look like humans.
 * Chuck Cunningham Syndrome: Rifleman after Juxtaposition.
 * Color-Coded Wizardry: The wizards, called Adepts, each pick a color, which matches their personality & type of magic.
 * Cool Horse: The book strongly features unicorns, which are portrayed very favorably.
 * Defeat Means Friendship: Stile and Neysa, Hulk, & Clef.
 * Depraved Bisexual: Tania, in the second trilogy (at first) & a good chunk of Proton's Citizens
 * Does Not Like Men: the first trilogy's Red Adept
 * Even Evil Has Standards: Purple insuring Brown was treated fairly in Phaze Doubt, as she treated him and Tan fairly as their jailer.
 * Finger in the Mail: The villains kidnap Clip, one of the protagonist's unicorn allies, and send him Clip's horn as proof.
 * Flowery Elizabethan English: Standard dialect of Phaze.
 * Freaky Friday: Mach and Bane's accidental swap which sets off the events of the second trilogy.
 * Fusion Dance: Happens at the end of Unicorn Point, in a BIG way.
 * God Mode Item: The Book of Magic and the Platinum Flute.
 * Great Big Book of Everything: The Book Of Magic
 * Green Rocks: Phazite, used to power the various spells.
 * Which, when taken to Photon, becomes the energy bearing Protonite.
 * Half-Human Hybrid: Thought to be impossible. But no one thought to check The Book Of Magic on the subject. Once they do along come Flach and Al.
 * Happiness in Slavery: Many Proton Serfs will do anything they can to stay on Proton.
 * Her Heart Will Go On: Subverted. A prophecy foretells that.
 * Then double subverted when
 * Hero Antagonist: The Translucent Adept in the second trilogy. Mach even more so, due to Honor Before Reason.
 * Heroic Sacrifice:, though we don't know it until much later.
 * High Heel Face Turn:
 * Hoist by His Own Petard: Tan and Purple's power grab (after their side had basically won) gave the good guys the opening to play their trump card.
 * Honor Before Reason: Comes up so regularly, the bad guys start to count on it.
 * Hypnotic Eyes: The Tan Adept possesses the magic of the Evil Eye, which grants him the power of Mind Control. His two children, a son who becomes the next Tan Adept, and daughter, Tania, also have this power.
 * Inevitable Tournament: nearly every major conflict is settled, once and for all, via the Great Game (or a variant, in Phaze).
 * I Have Boobs - You Must Obey!: The version of Tania in Proton doesn't have her Phase counterpart's Hypnotic Eyes, so when she desperately needs to convince a man to do something at a plot-critical moment, she tries the closest thing she can think of: flashing her breasts. It works.
 * It Only Works Once: Any specific Adept spell can only be used once, then variations have to be used.
 * Lawful Stupid: Piers Anthony's definition of "good." This is subverted whenever the good guys take advantage of Exact Words.
 * Literal Genie
 * Living Lie Detector: unicorns can test the truth of a person's words by spearing them with their horns. If the person spoke truly, they are left unharmed.
 * Magical Incantation: Stile's magic.
 * Magic A Is Magic A: Phazian magic has some very specific rules.
 * Mutually Exclusive Magic: But those rules are pretty much the only thing the various Adepts have in common.
 * Subverted by, the Robot Adept, whose ability with the Book of Magic is bound by no rules whatsoever, and in fact explicitly breaks several pre-existing rules (such as  ).
 * To be fair, the Book of Magic is described as the nuclear age of magic whereas the normal Adept magic is like cave men using tools.
 * Magic Music: Stile's magic must be invoked via rhyme and is strengthened by the use of music.
 * Clef's ability with the Platinum Flute allows him to do something that none of the other Adepts can: manipulate the Curtain that separates Proton and Phase.
 * Magic Versus Science: Only magic works in Phaze; only technology in Proton.
 * Meaningful Rename: Several characters choose their names from events and objects of personal importance (Stile, Rifleman, Clef).
 * Meaningful Name: Hulk, which was a Shout-Out. Also, Sheen and Mach. The third-generation characters, meanwhile, have names composed of a Portmanteau Couple Name from their parents--Nepe (Bane, Agape) and Flach (Fleta, Mach).
 * Merged Reality: The two worlds are eventually merged into one; as the characters are explicitly paired across both worlds (mirror-universe twin kinda thing), each pair merges into one being, and each pair has to time-share their body. Substantially easier for the heroes than for the villains, since heroes are used to putting the needs of others on par with or ahead of their own.
 * Mind Control: See Hypnotic Eyes, above.
 * Mix-and-Match Critters: Some native Phazites have animal heads on human bodies.
 * Morph Weapon: The Platinum Flute
 * No Name Given, Only Known by Their Nickname: The real/birth names of most of the human cast are never revealed. Also, serfs are required by Proton law to call Citizens "Sir", unless given explicit permission for other forms of address. Similarly, the Adepts in Phaze adopt their titles as their names: the Blue Adept is called "Blue", the Red Adept is called "Red", and so on.
 * No Nudity Taboo: Serfs on Proton are not allowed the privilege of wearing clothing. (There is an exception for safety gear.) This has made them indifferent to nudity and enhanced the appeal of sexy clothing.
 * One Judge to Rule Them All: How Stile won his harmonica duel against Clef, despite Clef giving what was clearly the superior performance. (The judges gave Stile the victory because he was a better *supporting* player; during their duet, playing with Stile produced a bigger improvement in Clef than playing with Clef produced in Stile.)
 * Ooh, Me Accent's Slipping: Stile and Blue tend to slip into their native dialects when speaking seriously or stressed.
 * Precocious Crush: Brown, towards Stile.
 * Prophecies Are Always Right / Prophetic Fallacy: In Juxtaposition, Stile was told he would be betrayed by "a young-seeming woman" and concludes it already happened, when Merle turned him in to the Citizen coalition. It turns out, however, that the true traitor was ...except in a Double Subversion, not only did she not know she was a traitor, but the betrayal actually ended up helping Stile in the end--. This last was another Prophetic Fallacy--everyone assumed.
 * Psychic Link: Mach and Bane, Flach and Nepe (Stile and Blue presumably can do the same but choose not to find out)
 * Retcon: The third generation protagonists get their nature and power level changed radically between when they were background and major characters.
 * Ridiculously-Human Robots: intentionally so.
 * Rhymes on a Dime: How Stile's magic works
 * Sacrificial Lion: . This, and the death of the equally innocent Bluette, led Stile into a Roaring Rampage of Revenge.
 * Self-Fulfilling Prophecy:
 * In a more series-wide sense, the Oracle does its best to make sure all its prophecies come true, aided by the fact that
 * Serious Business: In a world where losing a game of Rock-Paper-Scissors can mean getting booted off the planet, everything possibly included in the Great Game is treated as Serious Business. Also, oaths on Phaze (which are magically enforced).
 * Sex as Rite-Of-Passage: A werewolf gains adult status only after a ritual First Mating.
 * Smug Snake: the Purple Adept
 * Soul Jar:
 * Story-Breaker Power: Mach has no limits on his powers as the Robot Adept. He's kept in check solely by Honor Before Reason; while he personally supports Team Stile, he's agreed to play by the rules that the Adverse Adepts set instead of simply blasting them off the map by force majeure.
 * Suddenly Sexuality: The revelation, after seven books, that Brown is a lesbian, and given a relationship with Tsetse.
 * Technician Versus Performer: Stile (Performer) versus various other Technicians, most notably the musician Clef.
 * Take a Third Option: In Stile's duel with the Herd Stallion in Blue Adept, Stile uses the Platinum Flute's power to ensure a fair fight between them, rather than using the power of the Flue to curb stomp the Stallion (humiliating him and making things even worse for Neyssa) or fight him without magic (resulting in Stile's stomping/humiliation).
 * The Ace: Rifleman, from Juxtaposition
 * The Big Guy: Hulk
 * The Man Behind the Curtain: Brown, in her first appearance.
 * The Promise: Several, made via oaths or the Splash of Truth
 * The Scottish Trope: The "Triple Thee" (a binding and powerful love-oath in Phaze)
 * The Vamp: Merle, Yellow (after a youth potion)
 * There Can Be Only One: Established Adepts (read: Any adept who isn't Stile or one of his allies) tend to protect their positions by wiping out anyone who shows any real power within their specialty.
 * Took a Level In Badass: Clip (from exiled male in Juxtaposition to Herd Stallion in Out Of Phaze)
 * Tournament Arc: Most of Blue Adept and part of Juxtaposition involves Stile's journey through the Great Game.
 * Trilogy Creep: There are seven books.
 * Truth Serum: when someone swears something's true in Phaze, and they really mean it, a wave of rainbow light radiates from them.
 * Tyke Bomb: Flach and Nepe
 * Unobtainium: Phazite/Photonite
 * Unknown Assailant:
 * Villain Protagonist: Lysander in Phaze Doubt, though in actual deeds, he comes across as a Minion with an F In Evil.
 * Voluntary Shapeshifting: A unicorn can take up to three forms (unicorn, human, and a third of their choosing, usually a bird or some sort of predator) . Similarly, werewolves can voluntarily change between human and wolf forms at will, while vampires have human and bat forms.
 * The original Herd Stallion takes this a step further, and succeeds in mastering a fourth Form after Stile persuades him that it would be uniquely helpful in getting them out of their current situation:
 * What Kind of Lame Power Is Heart, Anyway?: Tan's Evil Eye grants absolute mind control; nifty, but other Adepts with more versatile powers can create spells to duplicate the effect in addition to the many, many other things they're capable of doing.
 * What Measure Is a Non-Human?: The unicorns, werewolves, and other shifters on Phaze, the self-aware machines on Photon
 * Why Am I Ticking?: In "Blue Adept", the hero is forewarned that the villain will try to force a magic bomb that will destroy him if he returns to Phaze with it., who realizes Just In Time what it really is.
 * Wise Beyond Their Years: Flach and Nepe
 * Word of God: That Red wasn't a Psycho Lesbian, but an asexual Psycho Misandrist.
 * Also, admitting that he turned Brown gay because he needed to balance the cast a bit.
 * To be fair, it wasn't even a retcon seeing as adult Brown had only had a handful of scenes, none of them really involving her sex life.
 * You Can't Fight Fate: Stile uses other people's Oracle prophecies to ensure his own survival.
 * This is made worse by the fact each person only gets one.
 * Serrilyan, who was prophesied to die after seeing the Sidhe three times. Clef then proceeds to pipe her soul to Heaven, despite her belief she didn't belong there.