Tunneler. The worm can burrow through solid rock at half its burrow speed and leaves a 10-foot-diameter tunnel in its wake.
Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 4 (3d10 + 4) piercing damage, and the target is grappled (escape DC 15). Until this grapple ends, the target is restrained, and the sand worm can't bite another target. Swallow. The sand worm makes one bite attack against a medium or smaller target it is grappling. If the attack hits, the target is swallowed, and the grapple ends. The swallowed target is blinded and restrained, it has total cover against attacks and other effects outside the sand worm, and it takes (4d6) acid damage at the start of each of the sand worm's turns. The sand worm can have only one target swallowed at a time. If the sand worm dies, a swallowed creature is no longer restrained by it and can escape from the corpse using 5 ft. of movement, exiting prone.