Considering its real-life tale of the 1916 lynching of a circus elephant and the event’s effects on those who either demanded or protested the execution, playwright George Brant’s Elephant’s Graveyard could rightly be labeled a drama. But it’s more accurately a horror story, and as evidenced by New Ground Theatre’s and director Debo Balogun’s electrifying presentation, that horror doesn’t come from a momentarily out-of-control pachyderm; it comes from human beings, from us, and our own worst impulses.