HBO's Game of Thrones panel, held in the largest auditorium at the San Diego Comic-Con and packed out, has revealed a lot of new information about the third season of the show. Season 3 of Game of Thrones will premiere on 31 March 2013 and will feature a significant number of new characters and actors, in addition to the already-announced Diana Rigg as Olenna Tyrell. Additional roles will include (and some more still need to be case, including Mance Rayder):
Orell is a wildling raider who possesses unusual abilities. He is a close advisor to Mance Rayder, the King-beyond-the-Wall. In the novels, Orell only has a minor role at the end of A Clash of Kings, where he is killed in a struggle with Jon Snow. Orell's casting and other tidbits suggest that Orell's role has been combined with that of Varamyr Sixskins. Why he is called Orell and not Varamyr, given the latter's far greater prominence (he is even, briefly, a POV character), is unclear.
Orell is being played by Mackenzie Crook. Crook is a familiar face from television and film. On TV he is best-known for playing the pedantic, military-obsessed Gareth in the original UK version of The Office. He also played Ragetti (the pirate with the wooden eye) in all three Pirates of the Caribbean movies.
Thoros of Myr is a red priest, a follower of the Lord of Light like Melisandre. Unlike Melisandre, Thoros is a drunkard and a warrior, more at home on the battlefield with his flaming sword (a normal sword covered in wildfire) than praying. He is a former friend and drinking companion of King Robert Baratheon.
Thoros will be played by Paul Kaye. Kaye is a well-known British comedian who debuted in the 1990s, most notably for his role as shock-interviewer 'Dennis Pennis'. In the early 2000s he moved into serious acting and has appeared on British dramas including Waking the Dead and Hustle.
Edmure Tully is the younger brother of Catelyn and Lysa Tully, and the eldest son and heir of the ailing Lord Hoster Tully of Riverrun. Though brave, Edmure is also untested on the battlefield and lacks the fine political judgement of his elder sister Catelyn.
Edmure will be played by Tobias Menzies. Menzies is best-known for playing Brutus on the HBO series Rome, and more recently has starred in the British spy drama Spooks.
Brynden 'the Blackfish' Tully is the younger brother of Lord Hoster Tully and the uncle of Catelyn, Lysa and Edmure Tully. An experienced soldier, knight and warrior, he is noted for his strategic skills and obstinate nature.
As previously indicated, Brynden will be played by Clive Russell, an experienced British actor. I'd suggest checking out his performance as Mr. Vandemar in Neil Gaiman's TV mini-series Neverwhere, where he is superb.
Selyse Baratheon, formerly of House Florent, is the wife of King Stannis Baratheon. Her health has not been good ever since the devastating Siege of Storm's End during Robert's Rebellion, and she spends most of her time restricted to a tower at Dragonstone (note: info from Season 2 of the HBO series, in the novels she is somewhat more mobile). She is an ardent worshipper of the Lord of Light and follows Melisandre's every word of advice.
Also as previously hinted, Selyse will be played by British actress Tara Fitzgerald, whose list of roles is far too large to mention here.
Tormund Giantsbane is one of the wildlings' chieftains and battle commanders. A hugely gregarious, outgoing man with a tremendous sense of humour, he also has a rough sense of honour and conscience. He is one of Mance Rayder's closest allies.
Tormund is played by Norwegian actor Kristofer Hivju. Hivju most recently appeared in the prequel to The Thing and is working on the new M. Night Shyamalan movie, After Earth.
Lord Beric Dondarrion is the Lord of Blackhaven, a small castle in the Dornish Marches. Beric has already appeared in Game of Thrones, when he was dispatched by Eddard Stark in Season 1 to apprehend Gregor Clegane just before the outbreak of the War of the Five Kings.
For whatever reason, HBO has decided to recast the role of Beric. He will now be played by Northern Irish playwright and actor Richard Dormer.
Jojen and Meera Reed are the children of Lord Howland Reed of Greywater Watch, one of Eddard Stark's closest friends and allies. The Reeds guard the Neck against enemies encroaching from the south, and have a hostile relationship with House Frey. The Reeds appear in the second novel, but were delayed until the third season due to cost reasons.
Playing Jojen is Thomas Brodie Sangster, unfortunately doomed to be known as 'that kid from Love, Actually' for life. He also starred in the Roman historical movie The Last Legion.
Playing Meera is Ellie Kendrick, best-known for playing the title role in the 2009 BBC mini-series The Diary of Ann Frank. She has more recently appeared in Upstairs Downstairs.
Shireen Baratheon is the only daughter of Stannis and Selyse Baratheon, and is now Stannis's sole heir since, as mentioned in Season 2, all of his sons have been stillborn. Shireen is a gentle, sweet child who has been cursed by the greyscale, a skin disease that kills many. Those who survive are marked by an area of skin - in this case on Shireen's face - that has turned grey and scaly,
Shireen will be played by Kerryn Ingram, who recently won a Laurence Olivier Award for her appearance in the musical Matilda.
Qyburn is a former maester of the Citadel who was invited to leave after performing some rather bizarre medical experiments on corpses. Qyburn has since made his living offering his knowledge and skills to whoever needs them, and in the War of the Five Kings some interesting opportunities have arisen for him to ply his trade.
Qyburn will be played by British actor Anton Lesser. Enormously experienced on stage, screen and radio, he recently appeared in the one-off drama The Man Who Crossed Hitler, the fourth Pirates of the Carribean film and was a recurring character on Primeval. On radio he is best-known for playing Lindsey Davis's signature character of Roman investigator Falco, in adaptations of five of her novels.
Anguy is a noted archer and marksman who frequently wins archery contests at tournaments. In the Song of Ice and Fire novels he won the archery contest at the tournament in honour of Eddard Stark and afterwards joined Beric Dondarrion's mission into the Riverlands. It is unclear if this will be the same in the TV series.
Anguy is played by Philip McGinley, a British actor best-known for his recurring role on Coronation Street as Tom Kerrigan.
Missandei is a young woman from the island of Naath, enslaved by pirates and sold in the flesh-markets of Slaver's Bay. She currently serves Kraznys, a slave-trader in the city of Astapor, as a translator.
Missandei is played by Nathalie Emmanuel, who recently left a long-running stint on the soap opera Hollyoaks.
Roles still to be announced: Mance Rayder, Daario Naharis, (presumably) Kraznys, Hoster Tully and possibly a few more. At this time I think it's likely that Oberyn Martell has been delayed until Season 4.