Castle Amber (1981)—an adventure for characters levels 3 to 6— contains an encounter in area #34 with…
…Catherine Amber, a level 13 magic-user who used the spell magic jar to transfer her life force into a piece of furniture. When the PCs enter, she possesses one of the PCs and attacks the remaining PCs with her spells. Apparently, Catherine cannot be reasoned with, having become "both evil and hopelessly insane due to her disembodied ordeal" (12).
The spell magic jar mentions only the spell dispel evil as capable of exorcising an invading life force, but that spell's only available to a level 10 or higher cleric! And Castle Amber proper's only level 10 or higher cleric is unlikely to help as he's a jerk… and he doesn't have dispel evil memorized anyway.
I'm okay with a Kobayashi Maru scenario or even a PC opting to make a noble sacrifice before control is complete (complete control taking about 5 rounds), and I'm okay with problems without immediate solutions—I mean, sometimes there is not a scroll of stone to flesh next to the medusa—, but this encounter? This seems absolutely guaranteed to kill at least one PC. Really, unlike many classic brutal encounters, the PCs have made no mistakes to deserve this encounter, nor have the PCs, for example, earned this encounter as a result of their carelessness or greed. This encounter just happens.
Is this actually a puzzle encounter, the solution eluding me because of my lack of familiarity with Basic D&D or because I overlooked something else in the module? Or is this just a way for the DM to kill off a troublesome PC?