The C.H.U.D. where once a group of homeless people known as the Mole People. In 2076 a greedy Toxic Waste Management firm called Amalgamated Refineries (their logo is on the barrels that litter the main home of the C.H.U.D.) decided that dumping their waste produces in the abandoned underground parts of Seattle would be easier and cheaper. The US government knew something was going on but by the time they were ready to investigate the war started and all was forgotten. The massive amounts of normal radiation slowly mutated the children of the homeless people living in the tunnels. When the bombs fell their fate was sealed. The group as a whole mutated and formed a hive mind. Now they live only to breed and feed. While they're not out to feast on human flesh they prefer it to other forms of meat and will actively hunt people to bring back to their home. They hunt by listening to the sounds of things above ground and wait until they are close to a sewer entrance.
Use the stats for a Trog but give them Area Knowledge: Seattle Sewers 5