[Endoperez]

There are sites that horror mark, but those mention it in their description.

EDIT: On second thought, I'm not sure if it was horror-marking or just some other annoying thing. I know some cause disease (Chillsick Swamp, Ink Pot End), and some others something different. Doom Cloud is the only one I remember right now, but I think it either curses or horror marks random units in the province it is in.