EA and Bioware have handed out some details regarding the DLC that comes included with the pre-order only Signature Edition (pre-order before January 11) of Dragon Age II. The Exiled Prince will otherwise cost 560 points (or equivalent we suppose) and is part of the $15 DLC value that is included with the Signature Edition.
"Our goal for the Dragon Age II DLC is to extend Hawke's journey and the Dragon Age universe by introducing additional characters with meaningful storylines and intense, dynamic missions," said Mark Darrah, Executive Producer of Dragon Age II. "Not only will 'The Exiled Prince' allow players to experience Sebastian's powerful revenge story, but they will also be able to utilize him as a follower throughout Hawke's rise to power in Dragon Age II."
Here is a description of The Exiled Prince, that adds a quest and a character to drag along on your adventures in Dragon Age II:
"The Exiled Prince" introduces the noble archer Sebastian Vael, with players joining him in the middle of his quest to avenge the brutal murder of his family. Sworn to the priesthood as a boy, Sebastian is forced to re-enter the viper's nest of princely politics when his family is brutally murdered, leaving him as the sole surviving heir. Banding together with Sebastian and his unshakable loyalty and excellent aim, players will choose to either avenge Sebastian's murdered family to reclaim his title or direct his holy vengeance on their enemies in Kirkwall. In addition to this action-packed storyline, players will also be able to enlist Sebastian as a follower throughout a majority of Dragon Age II.