Jon Snow doesn't take his Night's Watch vows in a godswood for nothing — he and his fellow northmen follow the "old gods," whom Bran will undoubtedly learn more about during his training with the Three-Eyed Raven in season six.
Where the religion is based: The North (particularly beyond the Wall)
What followers believe: Though few Westerosi still follow the Old Gods of the Forest, the Starks and their northern lieges believe that such powers existed before men came to the Seven Kingdoms — the Old Gods' original followers were the Children of the Forest. Sacred trees, weirwoods, act as vessels to see and hear prayers, and those gifted with special abilities (like Bran) were given them by various nature dieties.
Major religious themes: weirwood ("heart") trees, greensight
Who follows this religion: the Starks, the Reeds, the Umbers, the Boltons, other northern houses, and the Wildlings
