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 defences 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.
Physically, the Mawloc is an incredibly simple organism with most of its known bio-morphs geared solely towards burrowing into the earth where possible. It has six incredibly powerful limbs employed to gain traction underground, but they are small and lack the reach to be efficient in combat. Instead, it attacks by swallowing prey whole with its massive razor-toothed maw, or it pounds larger foes flat with its muscular tail before eventually devouring them as well. These victims are often digested within its stomach over several long days. Despite its immense size and mass, a Mawloc is incredibly agile and able to weave through incoming fire with fluid grace.
A Mawloc is almost entirely blind, and relies on a series of pressure-sensitive organs that run the length of its flank, which provide the Mawloc with a many-layered and ever-changing picture of the world around it. A Mawloc's senses are so delicate that it can absorb and interpret pressure waves as they travel through both solid and liquid matter. Mawlocs are able to detect even the slightest tremor, and intercept their quarry with unerring speed and accuracy. Added together, these qualities allows a Mawloc to home in on its prey even whilst burrowing through ground. The more regular and rhythmic the sound, such as the pounding thump of a terrified heart, the more likely a Mawloc will be able to orientate itself underground into emerging precisely beneath its prey. Thus it is a victim's fear that ultimately dooms them.
- Codex: Tyranids (5th Edition), p. 51