Not to harp on the D&D thing too much and too often, but I wonder if this is a level drain sorta deal. That shit was super obnoxious. I swear, a DM would probably never even bother using it if your party can actually do something about it the same day (even if just because it's a pain in the ass to figure out what all changed if someone got hit by it), but if they can't? It could take the rest of a campaign to get rid of it since you might need to find a specific healing item or some NPC healer of a high enough level, who probably required a donation or something.