After the Holocaust of 81 PC, Cremtosa was nuked entirely. Unbeknownst to the population, thousands of Cremtons and creatures dug and the remnants of a research institute and university fled into the underground, far beneath the surface of a city, for reasons lost to history. Archaeologists discovered they wanted to create their own attempt at a governmental nuclear shelter and preserve Cremtosese (including wildlife). Due to the nature of the nuclear holocaust and the people that went down, they tried building their own shelter similar to the ones set up by the government from scratch. However, this failed. Over the decades, the inhabitants of the makeshift shelter transformed all the lifeforms there into tunnel-dwelling ravenous abominations, and due to the diversity and mix of the lifeforms that were down there, this triggered more severe and twisted outcomes, and the creatures ended up becoming a vast mix of every species living down there. They were also influenced by the new atomic fungal environment of Cremtosa. The abominations were the strongest creatures in the galaxy. They bred extremely quickly, made hundreds of nests, and could swarm and devour even the most fearsome wildlife of the galaxy.
Living undisturbed by the surface-dwellers and not seeing the sunlight for nearly the next two-thousand years, they ruled the underground of Cremtosa. The creatures were basically hulking pack abominations that were a mix of Cremtons and dozens of native Cremtosese wildlife, that could tear apart and devour even the strongest creatures in the galaxy. They could dig for miles through the underground easily and set up hundreds of nests.
In 1983, the Cremtosese government discovered the abominations hundreds of miles below the surface. They named them "Tremors". Throughout the decade, they spent all their time and effort on removing the threat. However, Alidor Sotokom decided they would be useful. He ordered all tremors to be sent to the Andertierre Research Institute on the secret world of Lavink. Gigantic holding centres and facilities were built as extras to the facility to house the tremors, and by 1989, the expansion of the Institute was completed. The tremors were finished being lured out of Cremtosa and relocated to Andertierre by 1991. The remaining tremors were exterminated by a committed team, and any leftovers would be nominal, and would not have as much ability to breed, due to the population dive and the methods used by the team to lure them out (chemicals, biotech, etc.)
Beginning in December 1991, a month before the war began, the staff at Andertierre were tasked with housing two million tremors, and researching them extensively, and eventually, upgrading them. The military planned battle-ready tremors for April 1994. The aim was to deploy packs of thousands of tremors on enemy worlds, and then when they finished devouring the population and surrender came, command would trigger an implanted kill-switch inside the tremors and exterminate them all.
The plan was discovered by UNR spies in December 1993, and Task Force Comet was the main force in the intelligence war against Operation: Underminer, and discovered the location of the research centre. On the 28th March 1994, Andertierre and Lavink were attacked by the UNR. The project was henceforth abandoned, and all tremors were exterminated and drowned in molten lava after the UNR nuked the facilities.