Anollus

Corrode Metal. Any nonmagical weapon made of metal that hits the Anollus corrodes. After dealing damage, the weapon takes a permanent and cumulative -1 penalty to rolls. If its penalty drops to -5, the weapon is destroyed. Nonmagical ammunition made out of metal or wood that hits the Anollus is destroyed after dealing damage. The Anollus can eat through 2-inch-thick, nonmagical metal in one round.

Spider Climb. The Anollus can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Multiattack. The Anollus can attack 5 times: 4 with its tentacles and 1 with its bite.

Tentacle. Melee Weapon Attack: +13 to hit, reach 10 ft., 1 target. Hit: 24 (4d8 + 6) bludgeoning damage, plus 36 (8d8) acid damage. The target is grappled (escape DC 20) and restrained until this grapple ends. The Anollus has four tentacles, each of which can only grapple one target. At the start of each of the Anollus's turns, each grappled target takes an extra 21 (6d6) acid damage.

Bite. Melee Weapon Attack: +13 to hit, range 5 ft., 1 target. Hit: 16 (3d6 + 6) piercing damage, plus 18 (4d8) poison damage. If the creature is a medium or smaller creature grappled by the Anollus, that creature is swallowed, and the grapple ends. While swallowed, the creature has total cover against attacks and other effects outside of the Anollus, and it takes 36 (8d8) acid damage at the start of each of the Anollus's turns. If the Anollus takes 30 or more damage from a creature inside it, The Anollus 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 Anollus. If the Anollus dies, a swallowed creature is no longer restrained by it and can escape from the corpse using 10 feet of movement, exiting prone.