Greasel

The Greasel is a reptillian transgenic pest that haunts the sewers throughout the post-Collapse world. Originally created by VersaLife to serve as a guard animal, the Greasels proved to be very difficult to control, and when the Collapse hit and wiped out the security systems at VersaLife's various facilities, they escaped along with the Grays and the Karkians.

Resembling dragons, the Greasels are vicious predators with keen senses and the ability to expectorate a highly toxic venom. They mainly eat small live mammals, particularly cats, but they aren't picky; the unlucky scientists who became trapped in JC Denton's Sanctuary learned this the hard way, as a pack of escaped Greasels from the nearby VersaLife labs slowly hunted them until none of the scientists remained alive

In spite of the danger they pose, they are sought after by certain segments of post-Collapse society (the street value as of 2072 is around 375 credits.) In Lower Seattle, Greasel fights have become a popular attraction at the Greasel Pit Bar, where an intrepid trainer (or a smart gambler) can make considerable amounts of money with the right Greasel.