This is a hidden faction, you don’t start with any rep with them, not even netrual. They are located hidden in Deepholm, they also got a tabard, and reputation achievement.
To find them, go up north, it is marked on the map as “Therazane’s Throne” and you will find the quartermaster, is a small npc.
They sell mostly head enchants, there are even epic enchants everyone will need either for pve or pvp.
The Therazane’s quartermaster is an elemental as you can see in the picture, you can’t really click him or interact with him as you don’t have any reputation with Therazane.
You will need to start doing all the quests in Deepholm and eventually you will come across some quest regarding this faction, and get friendly, get the tabard.