18 (natural armor)
247 (15d20+90)
walk 50 ft., burrow 30 ft.
Con +11, Wis +4
blindsight 30 ft., tremorsense 60 ft.
15
The wurm can burrow through solid rock at half its burrow speed and leaves a 10-foot-diameter tunnel in its wake.
The wurm makes two attacks: one with its bite and one with its stinger.
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 wurm. A swallowed creature is blinded and restrained, it has total cover against attacks and other effects outside the wurm, and it takes 21 (6d6) acid damage at the start of each of the wurm's turns.
Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 19 (3d6 + 9) piercing damage, and the target must make a DC 19 Constitution saving throw, taking 42 (12d6) poison damage on a failed save, or half as much damage on a successful one.