The DLC will have you controlling a new character, Sebastian Vael, as his family is murdered. You have a choice of becoming a Batman-like character to avenge your family's death or you can also choose to fight the enemies of Kirkwall. The DLC will cost 560 BioWare points to download (about $7). Owners of the Dragon Age 2 Signature Edition get the Exiled Prince DLC for free.
Gallery: Dragon Age 2 Screenshots