Space-Time Vortex

Not to be confused with "Exvortex"

The term Space-Time Vortex (or simply "The Vortex") refers to a tunnel-like region of space, normally inaccessible.

By using said vortex, one can travel forward or backward in time, but can also hop between timelines. Those with especially high power can exit the vortex, exiting the universe altogether.

Mirai uses this a lot. He brought Setin through it, to basically show him how it is to travel through it.

The area inside the vortex is contorted: it does not correspond with the physical counterpart.

"If you don't know how to travel through the vortex, you can walk two steps and end up five lightyears away, or you can fly for days in here and only move a meter away." - Mirai

This spacetime vortex is a dangerous region, as there are specific movements you must make, otherwise you'd get stuck forever.

The safe movement is supposed to be spiral-shaped, "surfing" along the edges.

The concept is fairly similar to the vortex in BBC's Doctor Who.