Helm of the Forgotten Vanquisher

Helm of the Forgotten Vanquisher is a tier 6 armor token. It can be exchanged at Tydormu at the Hyjal Summit entrance for the following items:

It can also be exchanged at Soryn at the Isle of Quel'Danas for the following Season 2 PvP items:

Source
This item drops from Archimonde at the Hyjal Summit.