Nobody. Zexion is a Nobody, and hence feels no emotion. Charisma throws against Zexion have a disadvantage, and Zexion has a disadvantage on Charisma saving throws.

Master of Illusions. As the king of Illusions, Zexion uses mind tricks and traps to his full advantage in battle. Zexion's Book of Retribution floats around him during battle, and every turn creates a copy of itself. Zexion must always have at least one Book of Retribution, and can have a maximum of 7. Every Illusion Tome Zexion has gives him a 5% chance to reflect projectiles and magic aimed at him, and on top of this at the cost of some of the Illusion Tomes, Zexion can use his illusionary magic to mess with his opponents, and use stronger attacks.

Book Smack. Zexion commands his Illusion Tomes to attack a target within 5 ft. of himself. +3 to hit, deals 6 (1d6 + 3) bludgeoning damage. Number of d6's used is equal to the amount of Illusion Tomes Zexion has.

To The Shadows. Costs one Illusion Tome Zexion jumps into one of his Illusion Tomes, Zexion can still attack from inside the book, but he's completely safe from all damage while inside. The book Zexion is hiding inside has a distinct green glow, and can be damaged. It has 30 HP and 13 AC. Once the book is defeat, Zexion loses that Illusion Tome, and becomes staggered by the next attack that hits him.

True Fake. Costs 2 Illusion Tomes. Zexion rolls an Intelligence check, and if he rolls high enough, he copies an attack from an enemy that he has seen. This attack is now something he can use at any time at the cost of one of his Illusion Tomes. This true fake attack is indistinguishable from the normal attack.

Never Moved. Zexion shoots a bolt of black magic at a target within 15 ft. of himself. This bolt deals 17 (3d6 + 7), and if the target fails a DC 19 Wisdom check after they get hit, they'll be frozen in place. However, from the creature's perspective they'll still be moving and fighting, even though nothing they do is real. To break the spell, a teammate must snap them out of it with a DC 21 Intelligence roll.

Catching Gale. Costs one Illusion Tome. Zexion throws out a book up to 20 ft. away from him. After the next creature's turn, the book opens up into a giant Tornado. The Tornado pulls in all creatures within 30 ft. of it at the end of every turn by 5 ft. If something reaches the book, they not only take 45 (8d8) Force damage, but they also get trapped in the book, which makes them completely immobile until some rips them out of the book with a DC 19 Arcana check.

Illusionary World. Costs 3 Illusion Tomes, Zexion delves into the mind of a target within arms reach. The target must succeed a DC 27 Wisdom check, or Zexion will find his targets most haunting memory. From that point, Zexion will lock that target in a book, trapping them in the Illusionary World where they must experience that traumatic moment over, and over, and over until freed by a teammate. If there is anything that could damage the target in that memory, they're still able to be damaged by it just as badly as they would have been in the memory. If the target spends three or more turns in the Illusionary World, they need to start passing DC 20 Insight checks, or suffer 34 (5d8 + 9) Psychic damage per turn they spend in the book. Way too much time spent in the book can even permanently damage a person's brain.

Page Turner. Zexion grabs a target telekinetically that he can see within 40 ft. of himself. Both Zexion and the target must roll Perception, with whoever rolls the higher count winning. If the target wins, Zexion drops them and his turn ends instantly. But if Zexion wins, Zexion will rip a metaphorical page out of the target. This page being ripped out deals 29 (5d6 + 5) Psychic damage, and, in a forth wall breaking event, Zexion will single out an attack or ability that the target has, and remove that ability from the target's move set until the battle is over.

Perfect Disguise 2/Day Costs 2 Illusion Tomes, Zexion perfectly replicates the form of a humanoid he's seen the past. This includes shape, voice, personality, and even skills. Zexion's near perfect doppelganger can only be snuffed out by someone who's able to sense good and evil, as Zexion's doppelganger will almost always have a much more evil aura than the person he's replicating. If Zexion take 25 damage while disguised, his disguise will instantly break.

Shadow of Distortion. Zexion's Desperation attack, only usable while he's under half health. Zexion casts the arena into a pure darkness. Everyone in the darkness can see each other, but none of the surrounding area. a single Illusion Tome will float where Zexion stood before the attack started. The Illusion Tome will summon fake version of each person fighting Zexion. Each doppelganger will go for a different person they're fighting. If a doppelganger reaches a creature that isn't the one they're the doppelganger of, the creature must succeed a DC 19 deception check, or take 50 (5d10 + 22) Psychic damage, and switch bodies with the Doppelganger's creature. (Explained a bit less confusingly, if Player 1's Doppelganger reaches player 2, then Player 2 will have to take control of Player 1's character). The Doppelgangers are invincible and can't attack aside from their body switch ability, and can only be dispelled if the Illusion Tome is destroyed. The Illusion Tome has 40 HP, 15 AC, and can't attack, but has a 50% chance of reflecting projectiles. Once the book is destroyed, the darkness and the doppelgangers will disappear, but any body swapped creatures will stay in their swapped bodies until the end of the fight. After the attack ends, Zexion will reappear, his next turn will be skipped, he loses all but one of his Illusion Tomes, and he instantly staggers upon being hit.

Stagger. If you roll at least 7 over your chance to hit Zexion, he will stagger, being briefly stunned and allowing the attacker to attack again. If Zexion is staggered twice, he's launched briefly into the air, making him harder to hit again. If Zexion is staggered a whopping 4 times, he will break out of the Stagger and unleash one of 3 counter attacks chosen at random, and the attacker's turn instantly ends, no matter how many actions they have remaining. (Look for what attacks can be used as a counter under the attack section.) 

Nothing But a Mere Illusion. At the cost of one of his Illusion Tomes, Zexion can force another creature to reroll a skill check/dice roll. He can only do this once per turn, but can do it at any time during the turn, including outside his own actions.