Remina is a location in Monster Girl Quest Paradox
This Remina was destroyed during the Great Disaster, only a rift to Tartarus remains.
It is the place where the Great Disaster was caused. Uninterrupted by Ilias, a group of scientists intended to use Heinrich's sword to bring his spirit back. Unfortunately, because her blood was stained on the sword's blade, they instead brought back Black Alice from the original world, after the latter was defeated by Luka. Since she had both the powers of light and darkness integrated to the cellular level within herself thanks to the White Rabbit drug and her attempt to devour Ilias, she transformed into the Goddess of Chaos.
As of part 2, it has not yet been further delved into.