These millipedes mutated to an enormous size. They retained the ability to burrow underground, and preferred a subterranean environment, though would surface if hunger overwhelmed their natural instincts. The size they could reach was so vast, that it could destroy roads above in a manner comparable to an earthquake, as their burrowing left huge, vast, and unsupported tunnels underneath.
The creatures also developed four long mandibles, which were used to drag prey into their large mouths. To make full work of their mandibles, they would attack by lunging or biting, using their huge bulk to force prey into a corner, where it can be trapped and devoured.
The Grave Digger lays eggs in the ground and sewers typically in clutches of a hundred. When they hatched, the larvae; known as "Sliding Worms", would transform into new Grave Diggers themselves after a week.