"Game of Thrones" set a new ratings high Sunday night with its Season 2 finale, "Valar Morghulis."

The episode pulled in 5.1 million viewers for the night when including the encore, and for the first time the series attracted over four million viewers, 4.2 million in all, during its initial airing.

Based on author George R.R. Martin's "A Song of Ice and Fire" novel "A Clash of Kings," Season 2 has maintained stable ratings since its debut April 1. Initial episode airings have averaged 3.7 million viewers, with 10.4 million watching when factoring in all platforms and encores. This achievement places the series as the third most popular program in HBO's history.

As a result, HBO has already renewed it for a third season based on Martin's "A Storm of Swords" novel and extended series executive producers David Benioff's ("Troy," "The Kite Runner") and D.B. Weiss' contracts for two more seasons; although, the network has yet to announce a Season 4 pickup.

Filming for Season 3 will include a return to Belfast, Northern Ireland; Croatia, representing parts of King’s Landing; and Iceland.

“And we might even add a fourth country,” Weiss told EW.com.

In addition, the show is adding even more characters for Season 3.

“It’s important to point out that that we have the largest cast on television right now," Benioff explained. "We introduced dozens of new characters in Season 2. If you hurl 300 characters at an audience, the story collapses under the weight of too many faces, too many names, and too many subplots.

"We need to be just as mindful of the audience members who have never read the books as we are of the readers; the series will fail if we only appeal to those who already know the characters. So we try to be parsimonious about how many new roles we introduce to the story and when we introduce them.”

So who can we expect to join the show's swelling ranks? Although the producers promise it's not a complete list, here are some of the additions:

--Mance Rayder: The “King Beyond the Wall,” who leads a massive wildling host.

--Tormund Giantsbane: A wildling warrior.

--Jojen and Meera Reed: A young brother and sister whose family are allies with the Starks and who have links to the supernatural.

--Ser Brynden "The Blackfish" Tully: Catelyn Stark's (Michelle Fairley) uncle.

--Edmure Tully: Catelyn's younger brother.

--Daario Naharis: A seductive warrior from across the Narrow Sea.

--Beric Dondarrion: A knight and leader of Brotherhood Without Banners, who were initially deployed by Lord Ned Stark (Sean Bean) during Season 1.

--Thoros of Myr: A fast-drinking red priest who rides with Dondarrion.

--Lady Selyse Florent: The wife of Stannis Baratheon (Stephen Dillane).

--Shireen: Stannis’ disfigured daughter.

--Olenna "The Queen of Thorns" Redwyne: Margaery Tyrell’s (Natalie Dormer) stern grandmother.

"Game of Thrones," chronicles a treacherous clash among royal families to secure ultimate power of Westeros, a vast kingdom facing peril at every corner.

Season 1 of "Game of Thrones" received 13 Primetime Emmy Award nominations, including Outstanding Drama Series. It captured Emmys for Outstanding Supporting Actor in a Drama (Peter Dinklage) and Outstanding Main Title Design. Dinklage also won a Golden Globe for his performance.

The series was also nominated several times during the 2011 Airlock Alpha Portal Awards, scoring wins for Best Actor/Television (Sean Bean), Best Episode/Television ("Winter is Coming") and Best Series/Television.

Along with Benioff and Weiss, the series is executive produced by Carolyn Strauss and Frank Doelger. Martin, Vanessa Taylor, Alan Taylor, Guymon Casady and Vince Gerardis co-executive produce the show, with Bernadette Caulfield serving as a producer.

Read our review of the finale here.

"Game of Thrones" stars Dinklage, Lena Headey, Nikolaj Coster-Waldau, Emilia Clarke, Michelle Fairley, Maisie Williams, Sophie Turner, Kit Harington.