Arthropleura

Spider Climb. The Arthropleura can climb difficult surfaces, including along ceilings, without needing to make an ability check.

Poison Absorption. Whenever the Arthropleura is subjected to Poison damage, it takes no damage and instead regains a number of Hit Points equal to the Poison damage dealt.

Drowner. While submerged in water the Arthropleura's speed cannot be higher than 10.

Multiattack. The Arthropleura makes two Bite attacks,.

Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 17 (2d12 + 4) piercing damage.

Acid Spit. Ranged Weapon Attack: +6 to hit, range 60/90 ft., one creature, or metal object. Hit: If the target is a creature it takes 36 (6d10 + 3) Acid damage. If the target is a metal piece of armour or a weapon, the object takes a −1 penalty to the AC it offers (armour) or to its attack rolls (weapon). Armor is destroyed if the penalty reduces its AC to 10, and a weapon is destroyed if its penalty reaches −5. The penalty can be removed by casting the Mending spell on the armour or weapon. If the object is made of adamantine, the attack only hits on an attack roll of 20. If the object has the Unbreakable property or is an Artifact it is unaffected by this attack.