Unlock The Keeper and The Mistress:
To Unlock the Reaper and the Mistress from Dungeon Keeper 2 as playable characters in the Arena, just take the time to beat Vadrigar on the Fifth Tier, this will unlock a level called "The Keeper" (#5-5), beat this level and these to sweet characters will be yours to play as in the arena. (They will be after Zeal).

Level Skip:
During gameplay press and hold R1, R2, L1, and Select at the same tame and press X, Circle, Triangle, X, Circle, Square, Triangle, you will then automatically win the level.