As a Dungeon
Zero Isle North is one of the four (five in Explorers of Sky) dungeons on Zero Isle. It appears in Pokémon Mystery Dungeon: Explorers of Time & Explorers of Darkness and in Pokémon Mystery Dungeon: Explorers of Sky. Being one of the most difficult dungeons in the game, Zero Isle North is hard to complete.
Zero Isle North contains 75 floors, each floor containing Pokémon up to Level 90. The player cannot gain experience in this dungeon, therefore keeping them at the level they were upon entering. Only adding to the difficulty of the dungeon is the fact that no naturally found Pokémon can be recruited. Adding some EASE to this level is the notion that up to 48 items can be carried throughout it.