This is prolly gonna be incredibly vague, so I apologize.
When I was a kid, I remember watching a movie that involved a bunch of friends in a building of some sort, and some how, they'd each inevitably end up going downstairs and opening a small door. Each time that they'd open the door, some sort of bull/demon skull would come flying toward them, and then they'd become part of the horde of other possessed individuals.
Eventually it got down to a much smaller number (I believe it was just a guy and a gal that ended up surviving), and they had to make it up and over a wall before sunrise to escape with their lives.
I've been thinking about this movie off and on for the past decade, so if anybody could provide some closure, I'd be very greatly obliged.