Atop a Mountain of Corpses: Played with. Mulder and Scully fell into a pit full of dead and injured people that were dragged there by the monsters of the week. They tried to stack them so that they could get out of the pit.
Chekhov's Gag: Building a tower out of something unusual. First it's mentioned by the ridiculous couple of agents who are accompanying Mulder and Scully, then Mulder jokes about it with Scully, then they are in the hole in the woods building a tower out of human bodies.