Multiattack

The worm makes one Bite attack and one Tail Stinger 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 DEX save or be swallowed by the purple worm.<br>A swallowed creature is blinded and restrained, it has total cover against attacks and other effects outside of the worm, and it takes 21 (6d6) acid 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 CON save 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.

Tail Stinger

_Melee Weapon Attack:_ +14 to hit, reach 10 ft., one creature. _Hit:_ 19 (3d6+9) piercing damage, and the target must make a DC 19 CON save, taking 42 (12d6) poison damage on a failed save, or half as much damage on a successful one.

Thrash (Recharge 5-6)

The purple worm convulses its large body, smashing everything around it. Each creature within 20 feet of the worm must make a DC 19 STR save. On a failure, a creature takes 54 (12d8) bludgeoning damage and is stunned until the end of its next turn. On a success, a creature takes half the damage and isn't stunned.