Bonacon

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

Innate Spellcasting. The Bonacon's spellcasting ability is Wisdom (spell save DC 14). The Bonacon can innately cast the following spells, requiring no material components:

At will:  Thunderwave, Poison Spray (4d12)

Stink Aura. A 20-foot-radius sphere of yellow, nauseating gas emanates from the Bonacon. The cloud spreads around corners. Creatures inside the cloud have half cover against creatures outside the cloud.

Each creature that is completely within the cloud at the start of its turn must make a DC 14 Constitution saving throw against poison. On a failed save, the creature spends its action that turn retching and reeling. Creatures that don't need to breathe or are immune to poison automatically succeed on this saving throw.

Multiattack. The Bonacon makes two attacks: one with its bite and one with its horns.

Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 8 (1d8 + 6) piercing damage.

Horns. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 6) slashing damage.

Swallow. Melee Weapon Attack: +9 to hit, reach 5 ft., one Medium or smaller creature the Bonacon is grappling. Hit: The Bonacon swallows the target. The swallowed creature is no longer grappled but is blinded and restrained. It has total cover against attacks and other effects outside the Bonacon, it takes 14 (4d6) poison damage at the start of each of its turns. A Bonacon can have only one creature swallowed at a time.

If the Bonacon takes 20 damage or more on a single turn from the swallowed creature, the Bonacon must succeed on a DC 15 Constitution saving throw at the end of that turn or regurgitate the creature, which falls prone in a space within 5 feet of the Bonacon and is no longer blinded or restrained by it.