Time. A Periclitatus Species.
There are many realms in the universe. Realms represent a group of planes that are connected. This Realm’s planar structure is much like that of a bike wheel. Imagine the wheel with an infinite amount of spokes each representing a different plane. Each plane can extend infinitely so long as it doesn’t cross the “tire”(an area known as Dead Space. no plane is known to extend beyond it and the amount of worlds dramatically decreases as you get closer to Dead Space) or “axel(the core to which all planes are connected).” Because of this shape it’s relatively easy to jump between planes without tearing a hole in more worlds than I have hairs on my head. each is given an alphanumerical POE code, for organizational purposes.