Amalgamated Pest

Multiple Heads. The pest has four heads. While it has more than one head, the Pest has advantage on saving throws against being blinded, charmed, deafened, frightened, stunned, and knocked unconscious.

Whenever the pest takes 25 or more damage in a single turn, one of the pests separate from the main body and becomes docile.

Regeneration. The pest regains 10 hit points at the start of its turn if it has at least 1 hit point. If it takes fire damage, this trait doesn’t function at the start of the pest’s next turn.

Spiny Hide. At the start of each of its turns, the pest deals 3 (1d6) piercing damage to any creature grappling it or that it is grappling.

Multiattack. The pest makes as many bite or swallow attacks as it has heads (Max 3) When it's tail is available, it can use constrict in place of one of it's bite or swallow attacks.

Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) piercing damage.

Constrict. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) bludgeoning damage plus 5 (1d6+2) piercing damage. If the target is a Large or smaller creature, it is grappled (escape DC 16). Until this grapple ends, the creature is restrained, and the pest can't target another creature with this attack.

Swallow. The pest 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 frog, and it takes 8 (2d8) acid damage at the start of each of the pest's turns. The pest can have only one target swallowed at a time. If the pest dies, a swallowed creature is no longer restrained by it and can escape from the corpse using 5 feet of movement, exiting prone.