It was in the year 1273 that Furlongdor the Magnificent had his stroke of brilliance. Patrolling the borders of his.. slightly less than magnificent lands, he stepped in a rather foul dezien of the swamps. Most disconcerted was he when he raised his armored boot, only his foot came away, the boot rusted entirely away in the ooze-like thing. Like any wise knight, he struck it with his sword, only to lose the whole thing. Eventually, of course, he was forced to beat it to death with a large rock… and he was even more dismayed when the goop on the large rock dissolved a large hole in his breastplate. No, it was not until the ride back to his even more less than magnificent mansion, (okay, it’s down right run down), that he had the IDEA. He would build the goop into a weapon!
Many, many attempts later to integrate this into a sword, he finally settled on a giant stone axe, coated all in glass, even the handle, in order to protect it from the goo he paid the finest alchemists in all the land to refine from the rust-creatures at the edge of his swamp. Ugly, ungainly, and difficult to wield, no one would actually want to wield this axe… but for its other properties.
Set into the axe, at regular intervals, are places for glass ampoules to be attached. Filled with the ooze refined from the rust creatures, the ampoules break upon the first strike of the axe, spreading the goop out evenly over the stone of the blade. This goop, the refined digestive juices of the rust monster, quickly renders any armor the axe strikes into uselessness. It takes some time for the goop to wear away, however, without it, the axe is not much more than an really ugly club.