Athonian Tunnel Rats
Athonian Tunnel Rats are a regiment of Imperial Guard in Warhammer 40,000. They come from the world Athonos, which is a shithole where dozen of rival families constantly fight for power, with streets and sewers of their hydroponic gardens being a place of constant warfare. When Athonians are recruited by Imperium, they are already masters of urban combat and subterranean warfare, which is almost like the other Imperial Guard regiment... but let's not talk about it. They are mostly used against Chaos and Genestealer Cults. Athonian favorite weapons are Meltaguns, Flamers, and a light armor support in form of Sentinels and Chimeras, with which they fight in a caverns.