Creative director Patrice Désilets has left Ubisoft and abandoned the best-selling Assassin's Creed franchise, according to sources familiar with the situation.

Désilets has been with Ubisoft Montreal since its inception, working as a lead designer on the studio's early games like Hype: The Time Quest, a concept that originated from current EA Montreal studio manager Alain Tascan. His development career broke into the mainstream when he played an instrumental part in the resurrection of the Prince of Persia franchise, working as creative director on the massively popular Sands of Time release for PlayStation 2, Xbox, GameCube, and PC. Building on his success, Désilets then played an essential role in the creation of Assassin's Creed, a landmark new IP that has become the centerpiece of Ubisoft's catalog. Rather than wait to release the third installment after the highly successful sequel Assassin's Creed II, Ubisoft announced plans to take the Activision approach to game development with yearly iterations of its most popular brands. It is not currently known if this new direction affected Désilets' decision making.

The Désilets departure is a huge blow to Ubisoft Montreal, which recently lost the services of Far Cry 2 creative director and Splinter Cell mastermind Clint Hocking. Famed producer Jade Raymond, who also worked on Assassin's Creed for the Montreal team, recently left to assume control of the new Ubisoft Toronto studio. This could also undercut the public unveiling of Assassin's Creed: Brotherhood at E3 next week.

Désilets may not have the mainstream recognition of other major game developers who have departed their studios this year, such as former Infinity Ward heads Jason West or Vince Zampella, but he certainly commands that level of respect in industry circles. "I think there are three games that stand out above the rest of the pack in the remainder of this year. One is Call of Duty Modern Warfare 2, one is Uncharted 2, and the third is Assassin's Creed II," Metal Gear creator Hideo Kojima told Famitsu last year in an interview translated by 1Up. "I think a lot of recent Western games concentrate on style and the 'you are there' feel, but Patrice's games are still focused squarely on game design. The graphics have improved, but the system itself is a definite improvement over the last game. I think there are very few sequels like that. Any sequel needs to take in feedback from users and try to do what couldn't be done last time, but with Assassin II, they worked really hard to advance the real core of the game, the way you assassinate people. It's really great."

If Désilets chooses to stay in Montreal, he'll have several studios from which to choose. Warner Bros. Interactive, which is led by former Ubisoft Montreal studio head Martin Tremblay, recently opened a Montreal office. Electronic Arts and THQ also have studios that call the Canadian city home.

We contacted multiple Ubisoft employees for official comment on Désilets' departure, but its public relations team would only respond with, "We don't comment on rumor or speculation," adding that they were unable to contact anyone at the studio.

UPDATE: Ubisoft responded to our story with the following statement: "With his role on project essentially done, Patrice Désilets has decided to take a creative break from the industry and is no longer working on Assassin's Creed Brotherhood."