This looks to be a really interesting movie. Based on the Cassandra Clare novel, The Mortal Instruments: City of Bones opens on August 23, 2013 and stars Lily Collins, Jamie Campbell Bower, Robert Sheehan, Lena Headey, and Jonthan Rhys Meyers. The Mortal Instruments: City of Bones is the stoey of an average teenager who finds out she’s a descendent of half-angel demon hunters that keeps us safe called: the Shadowhunters.