When TV-only Game of Thrones viewers complain about the overwhelming number of characters currently populating Westeros and beyond, book fans can't help by sigh, Oh you sweet summer child. Because if you think there are a lot of players now ... well, you know nothing.

While we're a bit worried Game of Thrones is going to explode at the seams trying to accommodate the ever expanding cast of A Song of Ice and Fire characters, there are certainly some (more) book favorites we're eagerly anticipating seeing in the show. And now, thanks to writer George R. R. Martin, there are several characters who have been confirmed for the show's future.

Martin recently attended ConQuesT 44, a fan convention in Kansas City, and Tower of the Hand recapped his panel discussions. There's a lot of cool stuff in there, but most interesting of all was the news that the show is currently casting for three key characters: the Magnar, Mace Tyrell, and Oberyn Martell.

So, who are these characters? For those who haven't read the books (or need a refresher), here's a quick, non-spoilery rundown.

The Magnar. Styr, the Magnar of Thenn, is another Wildling leader, and part of Mance's army. In the books, he's the one who leads the raiding party that climbs the Wall. Obviously, Tormund has taken that role in the show, so it's a bit unclear exactly what we can expect from the Magnar in the show, but if he's anything like his book counterpart, he'll be an imposing presence.

Mace Tyrell. Mace Tyrell, Margaery's father, has already been mentioned on the show. Lady Olenna has painted a rather unappealing picture of her unimpressive son, and if he's like his book counterpart, he won't exactly subvert those low expectations.

Oberyn Martell. Expect to hear a lot of buzz about Oberyn Martell, AKA the Red Viper. He's a prince of Dorne (yes, we will finally meet some Dornish people soon!), and a giant badass. His family tree is fairly sprawling in the books, but we wouldn't be surprised to see the number of other Dornish characters thinned down for the show.

Which new character are you the most excited for?

Catch the next episode of Game of Thrones on Sunday, June 2 at 9 p.m. ET/PT on HBO.

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Source: Tower of the Hand

Rebecca Martin is an editor at Wetpaint Entertainment. Follow her on Twitter @BeccaDMartin.