The Gehenna Galaxy was the home galaxy of the Mavetians, the Kklxin and the Ch'chptk. It had a radius of 100,000 lightyears and was located approximately 3 million lightyears away from the Galactic Core Zone of the Crucible Galaxy. At its center lived a physical incarnation of the Titan Minos-Vaskus who took the form of a sentient black hole.
In the distance past, the Gehenna Galaxy was once flourishing with an amount of life comparable to the Crucible Galaxy. It was a major hub of the Empire of Arckas and at one point also hosted many megastructures that supported the Na'zrah Matrioshka brain. At some point, Minos-Vaskus wiped out the Mavetian civilization by emitting massive gamma bursts.
Around 5 million years before the Battle of Domum Regimen, the original Kklxin and Ch'chptk civilizations were at war over resources. Minos-Vaskus' attack during the era of the Arckasians rendered the overwhelming majority of planets in the Gehenna Galaxy uninhabitable. Planets that were viable for colonization were scarce. Eventually, it was agreed that the Minos-Vaskus was the mutual enemy, so the two teamed up to develop a superweapon that could kill a Titan. Their solution was the Galaxy Buster, a device that utilized their own version of the Anathema, femtobots originally built by the Arckasians to dismantle various celestial objects and megastructures to prevent the heat death of the universe.
The Galaxy Buster was launched at Minos-Vaskus. While the Kklxin and Ch'chptk succeeded in killing him, the results were far more than they bargained for. Not only did it completely and utterly destroy Minos-Vaskus, but the entirety of Gehenna's galactic core. This meant that the Gehenna Galaxy's entire structure would destabilize gravitationally causing its few inhabited worlds to undergo major climate shifts that wiped out entire ecosystems. Thus, the Kklxin and Ch'chptk decided to search for a new home in the Crucible Galaxy although they had to travel 3 million lightyears across Dark Space to get there. Thus, they survived in generation ships until they reached their destination.
At some point in the distant future, the Fadorva would have managed to reach the remains of the Gehenna Galaxy to terraform and create worlds there. Eventually, they would evolve into the Anarsaur species.