Rust monsters are subterranean creatures with an appetite for all sorts of metals. These unique creatures, though generally inoffensive, are the bane of fighters everywhere.
The average rust monster measures 5 feet long and 3 feet high at the shoulder. It has a strange tail that appears armor plated and ends in an odd-looking bony projection that resembles a double-ended paddle. Two prehensile antennae are located under the thing's two eyes. The hide of the rust monster is rough, covered with lumpy projections. Coloration varies from a yellowish tan on the underside and legs, to a rust red upper back. Rust monsters smell like wet, oxidized metal.
Rust monsters are placid by nature, but when they get within scent range of metal, they become excited and immediately dash toward the source. Rust monsters can smell metal up to 90 feet away. If the rust monster's antennae touch metal (determined by a successful attack roll), the metal rusts. Any affected metal rusts or corrodes and immediately falls to pieces that are easily eaten and digested by the creature. Metal weapons striking a rust monster are affected just as if the creature's antennae had touched them.