Unknown

Unknown is a special floor in that it can only be accessed after the player has collected all four seals locking its entryway. Once the player has collected them, they need only defeat Overlord on the fifth floor and use the northern exit after the battle to travel to it, as they would do to access any other floor.

Unknown is characterized by its dark, ominous atmosphere and especially difficult rooms. The walls appear old and cracked, and the dark background rhythmically pulses, showing silhouettes of damaged walls lit by what appear to be glowing pipelines. Rooms may contain new, difficult enemies or even mini-bosses that the player fought on previous floors as regular enemies. The area is so hostile that even tiles found within the rooms can come alive and attack the player. Shops and Upgrade Terminals do not generate here under normal conditions, though a Vault and Weapons Cache is guaranteed.

In addition to its unique form of access, the floor is also unique in that it houses many bosses that appear depending on which ship the player is using and on which difficulty setting they are playing.

When playing as any ship aside from Overlord or Chaos, the player will face the default Machine battle. As Overlord, they will fight the damaged Machine. As Chaos, they will fight the original Machine. When playing on Hard mode, they will face Monolith.

If the player possesses the Err: Integer Overflow cartridge or has unlocked Looping, the player will proceed to the seventh floor, Nowhere, after defeating the boss. Otherwise, the game will end.

Trivia

 * Under normal conditions, the player will not find a shop on this floor. However, if they possess the Cool Sunglasses cartridge, one will be generated. This is also the only way to see the Ascended One's dialogue, who will appear in the shop if they are present somewhere on the floor.