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

Blazing Body. A creature that touches the worm directly takes 10 (3d6) fire damage. On death, the body of the worm begins to cool reducing this damage by 1d6 every hour.

Multiattack. The worm makes two Bite attacks or one Bite and one Flare attack.

Bite. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 22  (3d8 + 9) piercing damage.

If the target is a Large or smaller creature, it must succeed on a DC 19 Dexterity saving throw or be swallowed by the worm. A swallowed creature is blinded and restrained, has full cover against attacks and other effects outside the worm, and takes 21 (6d6) fire damage at the start of each of the worm's turns.

If the worm 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, which fall prone in a space within 10 feet of the worm. If the worm dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 20 feet of movement, exiting prone.

Flare. Ranged Spell Attack: The worm launches five rays of fire as if casting the Scorching Ray. The target must make a DC 15 Dexterity save. On a fail, the target takes 14 (4d6) fire damage or half as much on a success.