Movie about a small mountain town.  Cops investigate a murder.  They find a room locked from the inside.  When the pry the door open there’s no one inside.  Turns out the mining in the mountain has awoken an ancient parasite buried deep in the mountain that has been killing off everyone in the town, except for a few survivors and the cops.  The parasite is much like The Blob (in that it attaches to and absorbs organic matter to increase its mass).  The parasite also gains the knowledge of the things it absorbs.  For centuries it absorbs bacteria and tiny organisms with no intelligence.  But after it started absorbing more complex organisms it became smarter and seeking out more intelligent prey.  It terrifies humans by using their worst nightmares as inspiration and creates real life monsters from the nightmarish ideas of the people it’s absorbed.  The military responds in force in an attempt to confront the situation, sealing off the town and sending in soldier/scientist teams to search the town.  The military, while putting up a valiant fight, is overwhelmed by the hellish creations of the parasite.  Soon the parasite has grown to an enormous mass, taking up the entire sewer system of the town and then some.  The cops figure out a way to kill it, electrocution it I think.  Parasite dead.  They leave the town behind them, wary but relieved.