So a friend of mine informed me recently that they had built a monster-hunter character, I believe it was a Ranger with favored enemy Abberation and all sorts of abilities enabling the character to be incredibly murderous. My inner Evil DM decided to inform them that this character was fairly vulnerable against Rust Monsters, as their primary melee weapon was a metal halberd, and it would be difficult to snipe off rust monsters with arrows in their natural environment, which, according to the Monster Manual, is ‘Underground.’ I imagine they’d inhabit mines, dungeons, and the underground equivalent of landfills or junkyards–all places where there would be a supply of metal readily available for consumption.
So, because my mind makes absurd leaps at times, I came up with the idea of a people who used the exoskeleton of Rust Monsters in order to create weapons, allowing them to effectively repel a better-armed and -armored force through guerrilla warfare.
Rust Monster Weapon Guys
Also known as RMWGs for ease and because I hate naming things.
The RMWGs live in a craggy, overgrown rainforest type environment, with plenty of old crumbling cliffs and really thick, obnoxious plants in the way of everything. The cliffs conceal plenty of caves–the homes of the rust monsters, but also the location of several valuable ores.
The RMWGs are a fairly nomadic, tribal people, who have long since learned to live off the land and survive in the jungle. Due to the jungle having all sorts of nasty carnivorous predators just like any other interesting D&D jungle, the RMWGs have also learned how to deal with said predators in sneaky and efficient, and have among their numbers many skilled outdoorsmen, hunters, and scouts. In 3.5 terms, this would roughly translate into large populations of Warriors, Adepts, Rangers, Scouts, Barbarians, and Druids as compared to other classes.
The Actual Weapons
I imagine the RMWGs as having Aztec-inspired weapons with better woodworking skill. Dovetail slots would be cut into a hardwood club, a matching dovetail would be carved into the sharp-edged scales, the scales would be slotted in and the club would be capped with another dovetail-jointed piece, this time with the joint running perpendicular to the previous joints.
Spears could also easily be made, as well as polearms along the lines of halberds or glaives.
Terrible vector graphics forthcoming. Poke the comments if you want schematics or something.
Possible Plot Hooks
(i hate plot)
So some intrepid explorer or another has discovered that there are valuable mines in the area. More Technologically Advanced Guys (MTAGs) want to capitalize on this discovery, so they have invaded the jungle and are attempting to secure an area of land for a fortress of some sort in order to be able to stripmine the jungle relatively unmolested. The RMWGs don’t take too well to the MTAGs stomping all over their homeland, but lack the capability to repel the reckless invaders by force, so they take to the trees and abuse the Tumble skill for all it’s worth. If the RMWGs are lucky, guerrilla tactics give them the advantage of surprise, the edge that they need to disarm(or) the MTAG forces before they are hacked to pieces.
The PCs could be hired by the MTAGs as mercenaries, they could be freelance gold diggers, or just explorers looking for a nice, easy, CR2 jaguar to stuff and show off.
Things I Haven’t Figured Out
I really have no idea how the DM would get the players to see the RMWGs’ side of things, unless they cleverly detangle the trope I’ve (re)built here by figuring out why the head of the mining camp is named Cortez.
Why do the RMWGs have Rust Monster Weapons? What possessed them to kill these critters and use their slimy scales as edges? Could be that the religious leaders of the RMWGs called on their deities for aid after a raid by the MTAGs, and were told that this could defeat their metal armor. Could be that the rust monsters were always the best source of edges, since the RMWGs lacked the ability to make iron weapons.
Why would the RMWGs kill the Rust Monsters in the first place? Due to the magic of Chemistry, I’ve discovered that the best way to make iron rust as fast as rust monsters do is to have very powerful oxidizers, especially acids, in contact with the metal. So if rust monsters can secrete all sorts of nasty acids, they’re unlikely to be edible.