I will throw a bunch player driven content ideas in the forum, here it goes:
Give players the
ability to sacrifice other players on an altar in dark rituals.
Sacrifice corrupted players and they become Wraiths:
- Necromancer: a fully corrupted player sacrificied by a Necromancer should become powerful Wraith. The corrupted player will play as a Wraith until killed.
- Conjurer: turns corrupted into Wraiths too, but the Wraith has to say within a certain range from the corrupted as his slave, if the Wraith flies away he will catch fire and slowly burn to death.
- Spellmancer: same as Conjurer
Corrupted players can only become Wraiths, they also can fly.
Wraith doesn't suffer any dampening
Wraith's kills on purple or red will help clearing a bit the corruption, if they kill a lot they will go back to non corrupted.

Non corrupted players could be sacrificed too, on an altar too, the ritual is still kinda dark.
Sacrificing non corrupted players:
- Necromancer: player becomes the ghost of himself/herself, semi-transparent, maybe white-ish, goes back to normal when dying while a ghost, burns if he runs away too far from the Necromancer
- Conjurer: turns people into elemental spirits, they can also fly, they go back to normal on death.
- Spellmancer: turns people into warrior fairies, or spirits of the forest, with colorful wings on their backs, they fly go back to normal on death.

A system in which you can sacrifice people and turn them into something else is for the player driven content and for player as other things or simply being strategic.
If it's too complicated then Wraiths only, but why be the same guy everyday?
Can you imagine a Necromancer bringing tens of players in the forms of Wraiths for an attack?
This has never seen before.