Jamie Campbell Bower and Lilly Collins star in The Mortal Instruments: City Of Bones, the adaptation of Cassandra Clare’s fantasy book series that Screen Gems picked up for an August 2013 release. Now Clare posted on her blog today more castings: Lena Headey will play Jocelyn Fray, newly Emmy-nominated Jared Harris will play Hodge Starkweather and Godfrey Gao is Magnus Bane. Robert Sheehan, Jemima West, Kevin Durand, and Robert Maillet also are aboard. Production is set to begin August 20 in Toronto. Constantin Film and Unique Features are producing the pic, which will be directed by Harald Zwart from Jessica Postigo Paquette and I. Marlete King’s adaptation. Constantin’s Robert Kulzer and Don Carmody are producing; Unique’s Bob Shaye and Michael Lynn are executive producing with Martin Moszkowicz for Constantin. The film, based on the first book in the series, is set in contemporary New York and follows a seemingly ordinary teenager (Collins) who discovers she is the descendant of a line of Shadowhunters, a secret cadre of young half-angel warriors locked in an ancient battle to protect our world from demons. After the disappearance of her mother, she must join forces with a group of Shadowhunters, who introduce her to a dangerous alternate New York called Downworld, filled with demons, warlocks, vampires, werewolves and other deadly creatures.

Related: Constantin Sets Lily Collins For Harald Zwart-Helmed ‘Mortal Instruments’