Cthonian

"Flowing tentacles and pulpy gray-black, elongated sack of a body... no distinguishing features at all other than the reaching, groping tentacles. Or was there—yes—a lump in the upper body of the thing... a container of sorts for the brain, basal ganglia, or whichever diseased organ governed this horror's loathsome life!"

- Brian Lumley, The Burrowers Beneath 

Chthonians are an alien species that resembles immense squids, with elongated worm-like bodies coated with slime. Despite their squid-like appearance, Chthonians are land-dwellers and are even harmed by water. Chthonians are powerful burrowers, live for more than a thousand years, and are protective of their young. It is said that a chanting sound accompanies every Chthonian, and that by such they can be detected while underground and unseen.