The Void

The void is a grayish space. It is an infinite plane that can be used to go between dimensions. The only problem is that portals to other dimensions close after 6 weeks but can be opened through the dimension's side. It can also be opened by god-like entities or if there is a crack in the void. A crack in the void is a portal that's almost closed. It takes a bit of force to open. If memories are wiped like in the reset timeline, the void gives them back but takes them back when you leave. There isn't gravity in the void. You can think of anything in the void and then it appears. So you need to think of a jet-pack to get around.

Futaba
Futaba lived in the void for a while while she was thinking. She also used this to slaughter people in different dimensions. Eventually she gained control of the Void. She was able to change the color and basically change anything of the void.

Reset Timeline (OPTU)
The portal used to be in Futaba's room but since the reset happened it moved the portal to Accumula's saloon. Futaba turned the part of the void near the portal into a hotel called Memory Lane. Anyone that enters it gets a room.