Monster Mondays began as a series of posts inspired by James Jacobs’ 10 goblin facts written for Pathfinder. Now, I’m creating new lore, encounters, unique NPCs and more for creatures in the Monster Manual. The goal is to provide habits, scene-setting tools, encounter hooks, and more variety, especially for monsters that don’t get quite as much love as dragons, beholders, mind flayers, and liches.
This week’s Monster Monday entry is a bit of a crossover with Monster Workshop. Going into this revitalized format, I made a list of OGL monsters, and I came up with four different article formats. The most challenging but also the most interesting is the Level Up/Level Down format. I rolled some dice, and a set number of monsters got drafted to get a leveled up or down statblock.
The idea is to take an existing monster with a low CR and beef it up a bit for an interesting low level boss or miniboss or to take a high CR monster and create a version that low level parties could face off against and survive. The rust monster is the first beasty to get this treatment.
The rust monster is an iconic creature with a CR of 1/2. The metal-eating monster can locate iron by scent within 30 feet, and it corrodes metal. It’s also faster than average with a speed of 40 feet. I want to boost it up to a CR 2 or 3, which should be pretty straightforward. We’ll boost the stats, but I also want to tap into Matt Colville’s excellent action-oriented monster suggestions, too.
I don’t want to mess too much with the rust metal trait or the antennae action. Those seem sufficiently complex mechanics on their own. It’s got a big, cool looking tail in the art, so I think a tail attack would be satisfying, and I’ll give it multiattack, too. I think the fact that it’s potentially doing permanent damage to weapons and armor every turn is probably enough of a substitute for reactions and bonus actions, but we are going to give it a suite of legendary actions.
It has big, grasshopper legs. I’m probably going to buff the size to large, and I think a big bug leaping right into the middle of your party has some spectacle to it. But I also want to play with the metal associations. I think our elder rust monster has Magneto powers. It may take a recharge, but it’s definitely going to be able to drag the party toward it via their weapons and armor. And the showstopper, I’m going to give it a “corrosive wave” where it tries to corrode all the exposed weapons within five feet. The wave will only go off once, and it’ll need a save-able DC.
That gives us a nice sequence. The rust monster leaps into the center of the group, drags them in with its magnetic aura, and then causes a bit of chaos with its corrosive wave.
Without further ado, your elder rust monster.
More dangerous than their smaller relatives, mutant rust monsters have grown in power deep within the earth. They are ill-tempered beasts that will gladly feast on flesh and blood when other sources of iron are less forthcoming.
Born in the Deep. Mutant rust monster crawl up from the deep places of the world. Some believe these rust monsters to be the results of magical experimentation. However, this seems to be the natural evolution of rust monsters exposed to a world’s core for long periods.
Magnetic Presence. As a mutant rust monster trudges along, all manner of small metal objects fly toward it, sticking to its carapace. A mutant rust monster that has eaten through a dwarven village will likely be covered in thimbles and belt buckles and half-corroded pots and pans.
Larger than Life. Those who have ventured deep into the Underdark whisper tales of massive rust monsters, even larger than these, with carapaces that shine with the remnants of arms and armor, skeletons pinned between their armor remnants and the beasts’ shells. Rumors tell of Underdark civilizations brought to their knees by the hunger of a rust monster titan.
Check out last week’s post featuring 3 cloaker NPCs.
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