The game was a horror-themed haunted house thing which mixed FPS gameplay with FMV. The story surrounded an American guy who inherits/explors(?) a big house in England. You begin to explore it and some English bird turns up to help you look around (a journo?). Certain doors were locked with glowing pentangles on the floor.
As you progressed you found hidden chambers etc and after a while you gained accoess to a "parallel universe" of doors which would take you to different parts of the house, and I think travel through time to the house's past. The plot, iirc, was about Templars guarding secrets of an occult nature and some new-age bad guy wizard dude who was following you.
At some point one of the weapons you got was a kind of shaman's staff that would fire blue fireballs (we called it the "Mystic Bazooka" at the time).
This was just before the time of proper 3D modelling of the monsters; they were still the sprite kind of nasty.