Thenn is a mountain valley located in the northernmost area beyond the Wall, hidden in the peaks of the northern Frostfangs. The Thenns consider themselves the last of the First Men.
A Dance with Dragons
Soon after Mance Rayder is defeated at the Wall and his free folk host broken, a dour warrior in fur and amber urges the survivors to come with him and take refuge to the valley of the Thenns. Though the Thenns had fled their valley for safety in the south, hundreds of other free folk still follow the warrior.