Neophron

Shapechanger. The neophron can use its action to polymorph into a Large giant vulture, or back into its true form. Its statistics, other than its size and speed, are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

Keen Sight and Smell. The neophron has advantage on Wisdom (Perception) checks that rely on sight or smell.

Magic Resistance. The neophron has advantage on saving throws against spells and other magical effects.

Multiattack. The neophron makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 15 (2d10 + 4) piercing damage. If the target is a Medium or smaller creature, it must succeed on a DC 16 Dexterity saving throw or be swallowed. A swallowed creature is blinded and restrained, it has total cover against attacks and other effects outside the neophron, and it takes 14 (4d6) acid damage at the start of each of the neophron's turns. The neophron can only swallow one creature at a time. If a humanoid dies while swallowed, it transforms into a ghast. At the start of its next turn, the neophron regurgitates the ghast into an unoccupied space within 10 feet. The ghast is under the neophron's control and acts immediately after the neophron in the initiative count. If the neophron takes 20 or more damage in a single turn from a creature inside it, the neophron must succeed on a DC 20 Constitution saving throw at the end of that turn or regurgitate the swallowed creature, which falls prone in a space within 10 feet of the neophron. If the neophron dies, a swallowed creature is no longer restrained by it and can escape the corpse by using 5 feet of movement, exiting prone.

Claw. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) slashing damage. The target must succeed on a DC 16 Constitution saving throw or be poisoned until the end of its next turn.