Catachan devil
Catachan Devils are insectoid creatures native to Catachan, a death world in the Warhammer 40,000 universe. Catachan Devils are scorpion-like in appearance with a series of segmented body sections and pairs of legs terminating in a long tail with a poisonous barb, which curves forward over the creature's back. As Catachan Devils grow, they develop more and more mid-sections and pairs of legs. A fully grown adult can have up to thirty sets of legs, reaching up to thirty metres in length.

The front legs of older male Devils become grossly enlarged, resembling scorpion claws. These mighty beasts are often dubbed "Fiddlers" in Catachan slang, and are feared for their ferocity and raw power. Catachan Devils are able to move with surprising speed for something of such large size, and are superbly adapted to move across a large variety of terrain. Once a Catachan Devil has captured its unfortunate victim, it will either shred it with its razor-sharp claws or sting it into insensibility with its barbed tail, before devouring it.

Catachan Devils are territorial, yet quite sociable creatures, tending to form nesting groups with others of their kind. These groups often contain several large male Devils, as well as a few dozen juvenile "Devilspawn." The entire nest will come together to defend their territory from any intruders, be it rival Devils, human colonists, or other predators, and have even been known to attack Imperial Guard tank companies. It has been speculated since the Imperium's first contact with the Tyranids that the Catachan Devils are the descendants of a long-lost Tyranid vanguard organism that has effectively become feral after being cut off from the Tyranid Hive Mind.