Boru

Keen Smell. The boru has advantage on Wisdom (Perception) checks that rely on smell.

Slug Climb. The boru can climb difficult surfaces, including vertically but not upside down, without needing to make an ability check.

Multiattack. The boru makes a bite attack and then uses its swallow ability.

Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 7 (2d4 + 2) piercing damage plus 4 (1d4 + 2) poison damage.

Claws. Melee Weapon Attack: +4 to hit, reach 10ft., one creature. Hit: 4 (1 d4 + 2) poison damage, and the target must succeed on a DC 13 Constitution saving throw or be poisoned for 1 minute. Until this poison ends, the target is paralyzed. The target can repeat the saving throw at the end of each of its turns, ending the poison on itself on a success.

Swallow. The boru makes one bite attack against a Medium or smaller target it is grappling. If the attack hits, the target is swallowed, and the grapple ends. The swallowed target is blinded and restrained, it has total cover against attacks and other effects outside the boru, and it takes 16 (4d8) acid damage at the start of each of the boru's turns. The boru can have only one target swallowed at a time. If the boru dies, a swallowed creature is no longer restrained by it and can escape from the corpse using 5 ft. of movement, exiting prone.