A rust monster is a large beetle that eats metal.1 Luma, who had never seen one before, proposed calling them Flaky Beetles, and Hazel agreed.2
Appearance
A rust monster is about the size of a person, large for a beetle, plated in chitin, with big bulging eyes and long, almost feathery feelers.2 It moves fast, with a rapid chitter of hard feet on stone.2 Its chitin is laced with the metal it eats, which makes it far tougher than an ordinary insect.2
Behavior
Rust monsters go for metal, and for the biggest piece of it they can find.2 A touch of their feelers rusts metal on the spot: it ate away a patch of Iva’s scale mail and rusted her spearhead.2 They try to snatch the heads of weapons with their feelers, and they bite.2 When hurt, one lashed out at the nearest metal within reach.2
They had eaten nearly every piece of metal in the sealed vaults they had reached, and had chewed through the bars of an old portcullis to get in.2 A larger one lay dead in front of three suits of animated armor.2 Hecate once spoke of creatures that coat themselves in iron, which Hazel had taken for a joke.2
History
Session 10
Three rust monsters attacked the party in Vault 14 of the sealed Underforge Vaults under Argentum, going for Iva and Hazel, the two wearing the most metal. Temerity, Iva, Hazel and Rhysaene killed all three.2 Luma mended Iva’s armor and spear, and Hazel cut some meat from one to eat later.2