Just like our old friends the Owlbear and the Bulette, this Rust Monster is a beast that was created based on an old bag of plastic toys from the dollar store. It was a clear and concise design, just like all the old monsters Gary Gygax and his friends used to spit out.
These things were simple, weird, iconic, and had a purpose. The Rust Monster’s express purpose was to slowly destroy the amazing gear that high level players had, forcing them to hunt down or create magical weapons and armor.
The Rust Monster does this with it’s huge antennae that have a full reach of five feet.They can smell and pinpoint any ferrous metal within 30 feet. This allows the Rust Monster to track that raw stuff down like a metal detector. For this reason, they can be a true boon for creatures that collect or need metal, but could be a bane for them as well. For if the Rust Monster finds the metal, it will just rust it and eat it, not do anything productive with it.
So maybe a muzzle and antennae covers would come in handy?
The Rust Monster mainly looks like a huge Cockroach, but it’s actually got a face like a Praying Mantis and Cricket style legs. This lets it move incredibly fast, and also helps intimidate other creatures. Their color is the same as the rust it eats. A dull copperish brown color, faded in places with pale and tan. The shell and chitin of it’s body is a swirl of marble colors that actually shines quite nicely.
The smell of a Rust Monster is actually fairly unoffensive, being similar to many cats that clean themselves. A simple scent that is bland and uninteresting. This is because the Rust Monster cleans all over its own armor and chitin with their long antennae, filled with flecks and specks of rust. The rust smooths the shell, then gets brushed off.
The solid plated body of the Rust Monster may look heavy, but the feeling of it is actually something more akin to a solid plastic bowl. Structurally, much more strong, but very lightweight and smooth. This is what allows the Rust Monster to run so fast. If you were to knock on it, there would be a hollow sound.
The Rust Monster is surprisingly quiet a good deal of the time. If you’re within 20ft of it, you can hear it chittering and spattering incessantly. This is the only noise it makes, and it makes it when it smells it’s food.
Some have said that the Rust Monster tastes an incredible amount like Shellfish. It is not an oceanic creature or a seafaring beast, but the high iron content shared by the two animals must be the correlation.
The easiest place to find a Rust Monster is one of incredibly high metal content. That much is obvious. Some of the places you’d expect to have metal sometimes do not. Old mines, for instance, don’t always have the Rust Monster in them, as they are usually devoid of their metals. The creature is much more common in caves or caverns with natural deposits of minerals.
Other interesting places to find them are in battlefields full of old equipment and weaponry, eating it all up, while Carrion Crawlers feast on the corpses. Perhaps in old abandoned festival grounds with clockwork Ferris Wheels and Roller Coasters. Even ancient fortresses with wrought iron gates, solid iron doors, and many cannons and weaponry. A Rust Monster goes where the food is, and that food is everywhere.
During a fight, the Rust Monster has natural and active defenses. Any weapons that hit it are going to take a bit of damage by being rusted up. It can also use its antennae to actively rust away armor or weaponry. Again, this only works on nonmagical weapons and armor, but would also work on regular metal items such as a lantern or a pickaxe.
The monster doesn’t really ever use tactics when it fights. It’s a hungry beast with one thing on its mind, which is metal. A Druid or Wizard without an ounce of iron on them could easily deal with the Rust Monster while it attacks the Fighter or Paladin.
A key tactic for DMs to keep in mind, is to have the Rust Monsters as mounts or beasts of burden for other, more intelligent creatures. Goblins, Kobolds, or even Orcs can be added to an encounter with a Rust Monster to make a harder fight.
Killing a Rust Monster won’t fix your weaponry. But, the chitin of the beast could easily be used to make armor that would rust the weapons of your foes. The antennae could even be turned into whips of some sort, that are able to do the same thing to armor and weapons.
Nobody will argue, the Rust Monster isn’t the most complex of beasts. But it’s simplicity is where it hides it’s creativity. You can do a real multitude of things with the Rust Monster, and all of them would make sense. Give it a top hat and name it Sir Eats’a’rust. Only a few players will roll their eyes at that.
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Image Sources: Wizards of the Coast
Roll a D12 to see what the Rust Monsters favorite food is.
10: Cold Iron