Bloat Beetle

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

Acidic Fluid. While it's acid spray is available for the beetle to use, any nonmagical weapon that hits it corrodes. After dealing damage, the weapon takes a permanent and cumulative -1 penalty to Damage rolls. If its penalty drops to -5, the weapon is destroyed. Non magical Ammunition that hits the creature is destroyed after dealing damage.

Death Burst. When a bloat beetle dies it explodes in a burst of acid, provided its Acid Spray attack is charged. All creatures withing 5 ft. of the beetle must make a DC 13 Dexterity saving throw taking 7 (2d6) acid damage or half as much on a successful save.

Bite. Melee Weapon Attack: +3 to hit, reach 5 ft., one creature. Hit: 4 (1d6 + 1) piercing damage.

Acid Spray (Recharge: 4-6). One creature within 30ft., or two creatures that are within 5 feet of each other and within 30ft. of the Bloat Beetle must make a DC 13 Dexterity Saving Throw, taking 7 (2d6) or half as much on a successful save.

Additionally if the target fails the saving throw and is wearing armour or holding a shield, their armour or shield (DM's choice) has a -1 penalty to the protection it provides. Magical shields and armour are immune to this effect. If a piece of armour's AC is reduced to 10 or if a shield's bonus is reduced to +0 it is destroyed.