Rust Monster

Medium beast, unaligned

Armor Class 14 (natural armor)
Hit Points 27 (5d8 + 5); Wound Threshold 7
Speed 40 ft.

13 (+1) 12 (+1) 12 (+1) 2 (-4) 13 (+1) 6 (-2)

Senses darkvision 60 ft., passive Perception 11
Challenge 1/2 (100 XP)


  • Iron Scent. The rust monster 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 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.


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.


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.

Section 15: Copyright Notice

The Creatures Rulebook for the Fateforge Role-Playing Game Copyright © 2021 Studio Agate.

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