The Key (2008)

Six friends descend on an abandoned building to shoot a documentary about its supposed haunted origins, but all is not as it seems. It turns out instead that the leader of the group actually brought them there to search for cursed buried treasure that his freemason grandfather had supposedly left. When one unfortunate soul opens a door to a darker dimension, a demon is released and begins to kill each of them one-by-one. Will anyone escape alive, or has "The Key" opened the door straight to hell?