The legs of the Swarm Host boast powerful muscles that allow them to vibrate at hypersonic speeds, not unlike the teeth of the Nydus Worm. Despite that, the creature couldnt burrow fast enough to adapt to shifting battlefield conditions. To correct this, a set of fragilealbeit regeneratingcapillaries was put into place. Now, when the Swarm Host digs, the capillaries break and the creatures acid blood softens the soil, allowing it to go underground in seconds.