Tunnel Worm

Tunnel Worms resemble the terrifying Purple Worms, but are smaller and much more docile. Their long body is brown and barbed, and their steel-hard jaws can crunch soil and rock to quickly burrow through the earth.
Dwarves, deep gnomes and drow elves living under The Skyward Peaks have learned to tame these worms to rapidly expand their subterranean realms.