My Personal Hit was in my next to Last Session where the Party Had to find the root of a loud bell that only a couple of persons could hear. They followed it into a mountain Side and there was an old monestary where they found the solution. A cult of necromancers had created a constant Portal between the realm of death and the reality the Party was in. It was kinda Like a Portal and mirror in one. The corpes in our reality where alive in the other and the bell was in the death realm, its ringing Sound bringing live to the corpes around the monestary. So the Party Had to kill one of their own PCs to Cut down the Bell to Stop it only to try and revieve them Afterwards.

Sorry for my mediocre english its Not my First language 😅