Rust Monster

Medium monstrosity, unaligned

Armor Class 14 (natural armor)

Hit Points 27 (5d8+5)

Speed 40ft.

Senses darkvision 60ft., passive Perception 11

Languages -

Challenge 1/2 (100 XP)

Traits

Iron Scent

The rust monster can pinpoint, by scent, the location of ferrous metal within 30ft of it.

Rust Metal

Any nonmagical weapon made of metal that hits the rust monster 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 made of metal that hits the rust monster is destroyed after dealing damage.

Actions

Bite

Melee Weapon Attack: +3 to hit, reach 5ft., one target.
Hit: 5 (1d8+1) piercing damage.

Antennae

The rust monster corrodes a nonmagical ferrous metal object it can see within 5ft of it. If the object isn't being worn or carried, the touch destroys a 1ft cube of it. If the object is being worn or carried by a creature, the creature can make a DC 11 Dexterity saving throw to avoid the rust monster's touch.

If the object touched is either metal armor or a metal shield being worn or carried, its takes a permanent and cumulative -1 penalty to the AC it offers. Armor reduced to an AC of 10 or a shield that drops to a +0 bonus is destroyed. If the object touched is a held metal weapon, it rusts as described in the Rust Metal trait.