Haunting, Perilous, Sinister, Threatening, Bleak
Dark Mysteries like Ambiance & Trepidation except it is less ambient and dark in terms of timbre and tonality. Many of the Scapes are more minimalistic and could go behind other sound effects. Think of walking through a haunted dungeon being followed by its inhabitants. Perhaps you are caught on a shadowy deserted spacecraft. It might also be what you hear on the menu screens of scary games.