Chomper

Swallow. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 8 (1d10+2) piercing damage.

Swallow. The Chomper makes one bite attack against a Large or smaller creature. If the attack hits, the target takes the bite’s damage, and the target is swallowed. While swallowed, the creature is blinded and restrained, it has total cover against attacks and other effects outside the Chomper, and it takes 11 (3d6) acid damage at the start of each of the Chomper’s turns.

If the Chomper takes 5 damage or more on a single turn from a creature inside it, the Chomper must succeed on a DC 16 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 5 feet of the Chomper. If the Chomper dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 5 feet of movement, exiting prone.