“I found her eyes, her skin, her delicate fingers... and at last, her face. Oh, this beautiful face.”
Quentin is a Blood Mage with considerable knowledge on necromancy driven insane by the death of his wife, prompting him to turn towards necromancy in order to get her back. He is encountered in Dragon Age II.
Involvement
Quentin is involved in the quest All That Remains. After searching for the missing Ninette, Hawke finds a templar by the name of Emeric involved in a mystery regarding the disappearance of multiple women throughout the city. After following a lead to a nobleman named Gascard DuPuis, it is revealed that Gascard is also searching for the killer because he murdered Gascard's sister.
Upon returning home, Hawke finds that their mother has gone missing. Hawke can ask Gascard to find Leandra using blood magic in Darktown, or head out to Lowtown to search for her with Gamlen by finding out from a young urchin boy that a wounded man asked her for help and she went away with him. Following a trail of blood, Hawke finds an underground cave that appears to contain multiple female corpses. Going to the end of the cave, Quentin is finally found with Leandra.
Quentin and Leandra
Driven insane by the death of his wife, Quentin had kidnapped and murdered different women in order to take parts of them and rebuild the likeness of his beloved. He saw his beloved's face in Leandra and that is what lead him to kidnap her. Finding his/her mother near death, Hawke kills Quentin and the abominations he summoned, including some desire demons which were possessions of Ninette, Alessa, and Leandra.
If Hawke takes Gascard with him/her to find Quentin, it is revealed that Gascard is actually Quentin's pupil looking for the secrets of necromancy, and the story of his sister is a lie. Quentin originally promised to teach Gascard but forsaken that promise after being paralyzed by his wife's death. If Varric is in the party, Gascard is automatically killed by him: Varric remarks that Hawke would have killed Gascard anyway.
In Quentin's lair there is a letter from someone in the Circle congratulating Quentin and indicating that some texts on magic have been left for him to pick up. The letter is signed "OrsinoO."
Quentin and his creatures are killed and Leandra dies in Hawke's arms. During the search, it is revealed that Quentin had a writing correspondence with someone with the initial "O", which is revealed to be Orsino in The Last Straw. Also, a reply letter from the First Enchanter of the Starkhaven Circle of Magi to Gascard DuPuis might suggest that Quentin might have been one of its escaped mages that fled either with or without Grace, Decimus and Alain after it was burned down.