Inner-Void

"'Everything you've seen up until now has been a frolic through the flowers. The Quantum Timeline has been safer ever since we've learned how to Quantum travel.'""'What makes you say that?'""'It used to be full of many, many more monsters, giant beasts with a ravenous sense of destruction, or evil aliens with noxious tentacles. Instead, we dumped them all here.' - Egonians"

Description
The Inner-Void is a secret, hidden area of the Quantum Timeline, discovered only by the Egonians. The void itself acts as a dimension of its own, albeit small for its size - with a large planet followed by two smaller ones. It has no stars, making it very dark on the planets, which include:

Jrak, the larger planet, contains millions of species on and in it. The planet has been continuously gaining monster for so long, a functional ecosystem has been built around it.

Loce, the second planet. It previously contained a prison for Zargathroth, until it was destroyed. The prison was rebuilt for miscellaneous criminals, however.

Teiv, the smallest planet. It's so pitch-black that all creatures living there are blind, and predators have developed an Anglerfish-like way of attracting prey, like Cellus, for example.

Chronology
The Quantum Lords do not know about the Inner-Void; the Egonians got to it first. They made a great effort out of keeping it hidden and cloaking it, so they can use it as a secret prison-realm for calamitous creatures.

Initially, it worked as planned, when the Egonians discover a race or species capable of mass extinction, they would exile it to one of the four planets. Unfortunately, it cannot lock away all life, after attempting to exile Zargathroth or the Extirpates, it seems that a being which is already capable of Quantum travel can eventually escape, given enough effort.

Two large prisons were built inside the Inner-Void, one solely for Zargathroth, and the other for Timeline-faring criminals serving a sentence. Zargathroth destroyed his prison nonetheless and escaped.

At some point after this, some monsters escaped the Inner-Void via unknown means and ended up in the Just Glow galaxy, dimension: MA.