Bring 3 Thunder Lizard Blood to Jorn Skyseer at Camp Taurajo.
Now, [player], you must face the great thunder lizards. So large are the beasts, the ground rumbles as they stomp across the plains. Take care as you fight them, for one false step and you may find yourself beneath their feet.
You will find the thunder lizards in the southern Barrens. They are known as Stormsnouts, Stormhides and Thunderheads. Return to me after you have bested them.