Rust Monster

Rust monsters are medium-sized aberrations in the roleplaying game Dungeons & Dragons. This insectoid beast is so-named because it devours metal.

Biology
The rust monster is a medium-sized aberration, typically standing at five feet long and three feet high. Its size makes it a suitable mount for humanoids of below-average stature.

Rust monsters move about on four segmented legs and their bodies are covered in bronze-coloured chitinous plates. Their tails end in angular crests that can instantly rust any metal object on contact and they sport a pair of long, feather-like antennae extending from their lower mandibles. The creatures use these appendages both as sensory organs and also to break down any metallic objects they find.

Behaviour
Rust monsters are unaligned, non-sentient creatures. While it is possible to tame them, not many adventurers do so because of their ravenous appetite for metallic objects. There is nothing more aggravating to an adventurer than finding out that his rust monster mount has gone and eaten his sword and shield, except for discovering that said mount has also eaten all of his gold so he cannot buy replacement items.

Rust monsters are capable of detecting any source of metal within a 90-foot distance. When they smell a metallic object, they will charge in its direction and attempt to seize it, even if said object is in the possession of another creature. Rust monsters are not aggressive towards other creatures, only attacking until a creature has dropped whatever metal items it is carrying. The rust monster will then happily devour the discarded object and pay its former owner no further attention.

Abilities

 * Darkvision - Rust monsters can see perfectly in the dark.
 * Scent - Rust monsters can smell metallic objects from up to 90 feet away.
 * Rust - A touch from a rust monster's antennae or tail will instantly cause metal objects to decay.