Lungers

A Lunger is a species of worm that are native to Ashgaurd. Bigger than houses and extremely heavy. They live in the ground and carve great tunnels deep below the earth. They do this mostly with their teeth, they are sharp enough to burrow through any stone. They are feral on their own but the Bullks have found a way to tame them. They fit the Lungers with armor to protect their soft body and even fit chambers onto the armor to carry Bullk troops.  They are used as troop transport,  siege weapons and as troops themselves.
Lungers are used in the current war and decimated many when the Bullks invaded. Wild Lungers still exist on Ashgaurd and even without armor are a great danger to anyone.