Extra Map 6 - Clear a random dungeon with 30+ floors, with Level 300+ enemies on the bottom floor

Extra Map 8 - Clear a random dungeon with 50+ floors, with Level 500+ enemies on the bottom floor, and have unlocked Extra Map 6

Extra Map 9 - Clear a random dungeon with 99 floors, with Level 1000+ enemies on the bottom floor, and have unlocked Extra Maps 6 and 8

(Use the Change character cheat with this also) Take ash and kill the green phantom. then talk to Marona. ask ker to make a character. Dont make one. quit and the green phantom will be back. repeat it and you can level up!

To unlock Extra Map 1, just beat the game once.
Extra Map 2 - Beat Extra Map 1
Extra Map 3, Etna, and Flonne (Fallen Angel form) - Beat Extra Map 2
Extra Map 4 - Beat Extra Map 3
Extra Map 5 and Laharl Beat Extra Map 4
Mid-Boss - Beat Extra Map 5
Myao - Beat Extra Map 8
Extra Map 10 and Baal - Beat Extra Map 9
Extra Map 7 - Beat Extra Maps 1-6