Rust Monster Matriarch

Medium beast, unaligned

Armor Class 15 (natural armor)
Hit Points 67 (9d8 + 27); Wound Threshold 17
Speed 40 ft.

STR	DEX	CON	INT	WIS	CHA
16 (+3)	11 (+0)	16 (+3)	4 (-3)	14 (+2)	7 (-2)

Senses darkvision 60 ft., passive Perception 12
Languages –
Challenge 3 (700 XP)

SPECIAL TRAITS

• Iron Scent. The rust monster matriarch can pinpoint, by scent, the location of ferrous metal within 30 feet of it.
• Rust Metal. Any nonmagical weapon made of metal that hits the rust monster matriarch 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 matriarch is destroyed after dealing damage.

ACTIONS

• Antennae. The rust monster matriarch corrodes a nonmagical ferrous metal object it can see within 5 feet of it. If the object isn’t being worn or carried, the touch destroys a 1-foot cube of it. If the object is being worn or carried by a creature, the creature can make a DC 13 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, it 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.

ACTIONS

• Antennae. The rust monster corrodes a nonmagical ferrous metal object it can see within 5 feet of it. If the object isn’t being worn or carried, the touch destroys a 1-foot 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, it 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.
• Bite. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 5 (1d8 + 1) piercing damage.
• Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 7 (1d8 + 3) piercing damage.
• Iron Spit. Melee or Ranged Weapon Attack: +5 to hit, reach 5 ft. or range 20/60 ft., one target. Hit: 5 (1d4 + 3) bludgeoning damage.

REACTIONS

• Parry. The rust monster matriarch adds 2 to its AC against one melee attack that would hit it. To do so, the matriarch must see the attacker.

LEGENDARY ACTIONS

The rust monster matriarch can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature’s turn. The rust monster matriarch regains spent legendary actions at the start of its turn.

• Iron Spit. The rust monster matriarch makes an iron spit attack.
• Bite. The rust monster matriarch makes a bite attack.
• Movement. The rust monster matriarch moves up to its speed without provoking attacks of opportunity.
• Antennae (costs 2 Actions). The rust monster matriarch uses the antennae action.

ABOUT

Rust monsters don’t form colonies, but particularly large and ferocious specimens, with a faster rate of egg-laying, are still referred to as matriarchs. Aggressive and clever, a matriarch can represent a significant threat on her own if she has the chance to build a nest in an area rich in oxidable minerals.

The rust monster is an extraordinary arthropod of significant size at maturity, known for its appetite for metal and other minerals that it consumes oxidized, if not completely rusted. Since their food is primarily found in cities and mines, the creatures like to roam around these areas, causing a lot of damage. Others wander through the caverns of the Netherworld, searching for their next morsel, whether alone or in a group.

Rust Monster Nests

A female rust monster will bring back as much metal as possible to her nest, where she’ll lay about twenty eggs. Her larvae will grow while gorging themselves on rusted metal, before taking their first molt, after which they’ll be left to their own devices. They’ll reach adult size after a few years.

Miners and mine owners are well aware of the scourge a growing population of rust monsters represents, so they’re quick to employ adventurers at the first sign of these creatures, to find their nest and exterminate them. This attitude of trying to annihilate a species is a problem in the eyes of those who are close to druidic traditions.

In their opinion, rust monsters have a role to play and a balance must be found.

SPECIAL OPTION

When using this option, oxidation is not an absolute and limitless phenomenon. It’s a chemical process that can transform certain metals and stones, but not all. For example, gold and mithral don’t oxidize. On the other hand, iron, silver, copper, and bronze are very vulnerable to oxidation and, therefore, appetizing to rust monsters. Bauxite-a red soil that is plentiful in some desert lands-is an example of a type of naturally oxidized dirt, making it an ideal terrain for a population of rust monsters.