Diana Rigg, Natalie Dormer Diana Rigg, Natalie Dormer

There's nothing like a dame when HBO is casting for Game of Thrones.

The fantasy drama has cast legendary British actress Dame Diana Rigg to play Olenna Tyrell, it was announced at Comic-Con Friday. The Daily Mail first reported the news. Olenna is the grandmother of Margaery (Natalie Dormer) and Loras Tyrell (Finn Jones) and is also known as the Queen of Thorns, not only because the rose is on the Highgarden coat of arms, but also because of her rather caustic tongue.

Catch up on all the Comic-Con news

Rigg is best known for playing the assertive Emma Peel on the 1960s British spy series The Avengers and Countess Teresa di Vicenzo in the 1969 James Bond film On Her Majesty's Secret Service. She joins a slew of new cast members that were also announced Friday including: Lady Catelyn's uncle Brynden "The Blackfish" Tully (Clive Russell), Missandei (Nathalie Emmanuel), a new servant to Daenerys; the wilding Orell (Mackenzie Crook); Stannis' daughter Shireen Baratheon (Kerry Ingram); crannogmen siblings Jojen and Meera Reed (Thomas Brodie-Sangster, Ellie Kendrick); Beric Dondarrion (Richard Dormer) of the Brotherhood Without Banners and red priest, Thoros of Myr (Paul Kaye).

HBO also announced a few more names: Kristofer Hivju as wilding warrior Tormund Giantsbane; Philip McGinley as fellow Brotherhood member Anguy, an archer; Tara Fitzgerald as Stannis' reclusive wife Selyse Baratheon; Tobias Menzies as Catelyn's brother Edmure Tully; and Anton Lesser as Qyburn, a former maester of the Citadel, who was stripped of his chain many years ago.

Author George R.R. Martin, whose books are the basis for the HBO series, moderate the panel and joked, "So clearly I have to start killing these characters to make room for new ones." The author is known for killing of beloved characters in the series.

Game of Thrones is currently shooting Season 3, which will premiere on March 31, 2013 on HBO.