The Between

An extradimensional place that harbors energy that is not understood by science. A flood of color and energy that houses the different realities. Effectively infinite, but it can be left by going up to the Beyond.
The Between is filled with a sentient entity that is perceived as a flood of colors. This entity protects and nurtures the realities with in it. When in the Beyond, this entity is seen as a cloud of color without any clear borders.