Mawlocs

A Mawloc is a huge, worm-like Tyranid organism that acts as an outrider for a Tyranid swarm. They are burrowing creatures that travel deep underground to bypass enemy defenses and then emerge behind enemy lines to run rampant through supply lines, command posts, or artillery batteries, only to vanish back underground to evade retaliation. Severe earth tremors are the only warning of a Mawloc attack.