Which Character Do We Really Need To Meet In Game Of Thrones Season 5?

Every year, Game of Thrones introduces a few new characters to its massive cast. This year, it's Prince Oberyn, the Magnar of Thenn, and a couple others. But which book character absolutely must be introduced in season five, for the whole thing to work? And who do you want to play him or her?

Please include a picture of your chosen character (there's a lot of artwork showing even minor characters from A Song of Ice and Fire — but please credit the artist.) And please mention which actor you'd like to play them. And also, why he or she is so vital to the story, moving forward.

Warning: Massive book spoilers are going to be involved!

Top image: Victarion Greyjoy, art by Matt Olson. We probably won't meet all of Theon Greyjoy's massive family, and we may not even see the Kingsmoot that happens in the books. But Victarion is fairly important, since he's apparently supposed to meet up with Daenerys in Meereen.