Styr

Styr is a character that will debut in the fourth season. He was not present in Season 3 but leaked casting auditions indicate he's being cast.

In the books
In the A Song of Ice and Fire novels, Styr is one of Mance Rayder's lieutenants and the Magnar - "Lord" in the Old Tongue of the First Men - of the Thenn people, a clan of Free Folk established in a valley north of the Frostfangs. In the series, much of his plotline from A Storm of Swords is taken by Tormund Giantsbane - including being mistaken by Jon Snow for Mance, and leading the climb over the Wall.