This place is an otherworldly realm connected to the Sea Ark hotel. After defeating Manitou and making a clear save, upon loading the protagonist will be back at the HQ with a new message on Summoner Net regarding a power surge at the upper levels of the Sea Arc. Taking the elevator up to the 11th floor and entering the door will lead into this dimension. The Room of Spinning Wheels contains Sukeroku, who tells you this place is a separate realm from Amami City and that he is here to observe your trials in these corridors.
The trials are divided into five sections, with a puzzle in each. At the end lies a powerful demon who must be defeated to receive a manji that will open the way to the next room. The five bosses are King Frost, Mara, Lilith, Lucifuge, and finally the superboss Beelzebub. Once Beelzebub is defeated, a door named simply "??????" will enable the player to begin New Game Plus.
In addition, this area is unique in that it is the only place where Reapers and UMAs can be encountered and recruited.