Tunneler. The wurm can burrow through solid rock at half its Burrow Speed and leaves a 10-foot-diameter tunnel in its wake.

Contaminated Gullet. A creature swallowed by a wurm gains one level of contamination each time it takes acid damage while inside the wurm.

Bite. Melee Attack Roll: +14, reach 10 ft. Hit: 22 (3d8 + 9) Piercing damage. If the target is a Large or smaller creature, it has the Grappled condition (escape DC 19), and it has the Restrained condition until the grapple ends.

Breach. The crater wurm utilizes its full movement. While doing so, it can enter large or smaller creatures’ spaces. Whenever the wurm enters a creature’s space, the creature must succeed on a DC 19 Strength saving throw. On a successful save, the creature can choose to be pushed to the side of the wurm’s space. A creature that chooses not to be pushed suffers the consequences of a failed saving throw.

On a failed save, the creature takes 35 (10d6) bludgeoning damage, and is pushed 10 feet and knocked prone. After finishing its move, the wurm can make one bite attack against a prone target as a bonus action.

Swallow. Strength Saving Throw: DC 19, one Large or smaller creature Grappled by the wurm (it can have up to three creatures swallowed at a time). Failure: The target is swallowed by the wurm, and the Grappled condition ends. A swallowed creature has the Blinded and Restrained conditions, has Total Cover against attacks and other effects outside the worm, and takes 17 (5d6) Acid damage at the start of each of the wurm’s turns.

If the wurm takes 30 damage or more on a single turn from a creature inside it, the worm must succeed on a DC 21 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, each of which falls in a space within 5 feet of the worm and has the Prone condition. If the worm dies, any swallowed creature no longer has the Restrained condition and can escape from the corpse using 20 feet of movement, exiting Prone.