Darkness. The corrosion crawler larva spreads magical darkness in a 10-foot radius.
Metal Scent. The corrosion crawler larva can pinpoint, by scent, the location of any metal within 30 feet of it.
Corrosive Form. A creature or object that touches the corrosion crawler larva or hits it with a melee attack while within 5 feet of it takes 3 (1d6) acid damage. Any nonmagical weapon that hits the corrosion crawler larva 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.
Nonmagical ammunition that hits the corrosion crawler larva is destroyed after dealing damage.
Spider Climb. The corrosion crawler larva can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.
Drop. The corrosion crawler larva attempts to drop on any object containing metal. If the object is being carried or worn by a creature, that creature must succeed on a DC 11 Dexterity check to avoid this effect.
Once the larva has dropped onto an object it is attached and can only be removed by a creature using their action to remove it by succeeding on a DC 11 Strength check. At the beginning of every round the larva is attached it makes its bite attack on the object.
Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target object. Hit: 1 piercing damage plus 3 (1d6) acid damage. In addition, any nonmagical armor that is targeted is partly dissolved and takes a permanent and cumulative −1 penalty to the AC it offers. The armor is destroyed if the penalty reduces its AC to 10. In addition, any nonmagical weapon that is targeted 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. In addition, if any nonmagical container containing coins should be destroyed by this attack, the larva may use its action each turn it remains attached to feed on 1d4 coins from the container, starting with electrum coins, followed by copper, platinum, gold, then silver.