After playing a vampire-slaying werewolf in all three Underworld films, critically acclaimed British actor Michael Sheen is joining the cast of New Moon, the follow-up to 2008's teenage vampire romance, Twilight. Sheen joins American actress Dakota Fanning and Sweeney Todd teen Jamie Campbell Bower as the latest additions to the New Moon cast; all three will portray members of the ancient and deadly Volturi, who appear not only in New Moon but also in subsequent Twilight novels.

Sheen will play Aro, one of the leaders of the powerful Italian coven known as the Volturi, in director Chris Weitz's take on the Stephenie Meyer novel. The casting news comes courtesy of Variety, though the trade does not specify Sheen's role as Aro by name.

Production is already underway in Vancouver on the Twilight sequel, which will see the return of cast members Kristen Stewart and Robert Pattinson as Bella Swan and Edward Cullen, respectively. Fellow Cullen clan players Nikki Reed, Peter Facinelli, Elizabeth Reaser, Ashley Greene, Kellan Lutz, and Jackson Rathbone are also returning, along with Billy Burke as Bella's father and Taylor Lautner as the Quileute local Jacob, who will play a larger part this time around.

Sheen will reportedly play Aro, who along with fellow ancient vampires Caius and Marcus, leads the powerful Italian coven known as the Volturi. Aro, the assertive leader of the three, is a rare vampire with special powers similar to Edward and Alice, and can read any person's mind through physical contact.

Although the Volturi only appear toward the end of Meyer's New Moon novel, the role of Aro is significant in later installments of the Twilight saga as the Volturi play a larger role in Bella and Edward's lives. As such, the addition of Sheen (and the previously announced Dakota Fanning, who will play Aro's henchwoman, Jane) gives the Twilight sequel -- and by extension, any future films, providing the screen adaptations remain faithful and roles are not recast -- an added credibility boost.

New Moon is due in theaters November 20, 2009.