'The Mortal Instruments: City of Bones' Trailer: Cassandra Clare's Commentary

Welcome to the "City of Bones." If you missed your invitation last night, MTV News is taking you inside the secret world of the Shadowhunters with the first trailer for the big-screen adaptation of Cassandra Clare's best-selling novel… And by the angel, what a trailer it is! Despite having wrapped production mere days ago, this teaser offers a surprisingly robust look at heroine Clary Fray's (Lily Collins) journey to uncover the hidden truths about her family and her own special gifts.

The trailer opens with the Brooklyn teen inside the Shadowhunter Institute, where caretaker Hodge (Jared Harris) is explaining the legacy of the demon-destroyers, how they fit into the battle between good and evil. Cut to impossibly beautiful Jace Wayland (Jamie Campbell Bower) filleting a foe at Pandemonium—an act only Clary can see, hinting at her latent abilities.

But why am I doing all the explaining when we can turn to the source? We called up author Cassandra to get her commentary on the trailer; after all, she's not only the author of "City of Bones," but she spent a significant amount of time on the Toronto set, taking in all the behind-the-scenes secrets that she's sharing here. Click play on the video below to hear her talk about CGIed demons, runes, the fight sequences and more!

What do you think of this first trailer for "The Mortal Instruments: City of Bones"? Tell us everything in the comments and on Twitter!