Extra Map 1: Successfully complete the game
Extra Map 2: Complete Extra Map 1
Extra Map 3: Complete Extra Map 2
Extra Map 4: Complete Extra Map 3
Extra Map 5: Complete Extra Map 4
Extra Map 6: Complete a random dungeon with over 30 floors and enemies over level 300 on the bottom floor.
Extra Map 7: Complete Extra Map 1 through 6
Extra Map 8: Unlock Extra Map 6 and also complete a random dungeon with over 50 floors, and enemies over level 500 on the bottom floor.
Extra Map 9: Unlock Extra Map 6 and 8 and also complete a random dungeon with 99 floors, and enemies over level 1000 on the bottom floor.
Extra Map 10: Complete Extra Map 9