How do you get the searing gorge key in World of Warcraft

In a small mountain cleft in the South-East part of the Searing Gorge is a large thunderlizard called Margol the Rager. This is a level 43 mob, that used to be Elite but isn't anymore. He drops a charred horn with a piece of an axe in it, which starts a quest. Follow the quest line and you will be awarded with the key.