The Mortal Instruments: City Of Bones, the adaptation of the first of Cassandra Clare’s novels, opens August 21 in the U.S. and the UK. The trailer below is a slightly different take on the first which was released last November. Lily Collins stars as Clary, a seemingly ordinary girl who discovers she is the descendant of a line of Shadowhunters, a secret cadre of half-angel warriors locked in an ancient battle to protect our world from demons. Jamie Campbell Bower, Lena Headey, Aidan Turner, Jonathan Rhys-Meyers, Kevin Zegers and Jared Harris also star. Director Harald Zwart is starting the sequel, The Mortal Instruments: City Of Ashes, this fall.