Jacob Brogab in Slate:
When I think back to the demons of my childhood, I almost always linger longest on the rust monster. Though it resembled a crudely drawn armadillo, it was the size of a mountain lion. Other, more dangerous, beasts lived in the caves where I found it; there were neither claws on its three-toed feet nor fangs in its mouth. Still, it was a frightening creature: Tentacular whiskers, each longer than a human arm, emerged from its smirking maw. Those unearthly appendages probed the empty space between us, tasting the air. Whenever they touched a metal object—my shield, my armor, my sword, my dagger—it would immediately oxidize, crumbling into a useless pile of reddish flakes. And then the rust monster would feed.
I met this creature in a solo adventure that accompanied the 1983 Dungeons & Dragons basic rule set my mother brought home from the library. Before our fateful encounter, I would ably fight off less-challenging antagonists like giant rats and angry goblins, but the rust monster, which presided over a cache of precious gems, undid me. It wasn’t the beast’s own stats—its formidable hit points or the difficulty of piercing its armored hide—that frightened me, but its ability to literally eat away at my own protective gear. Our struggle would leave me defenseless. I’d flee the cavern with only my fists to fight back against the other horrors that lurked in the dark and only my thin skin to protect me against their jagged blades.