Slay 15 Crushridge Warmongers, then return to Marshal Redpath in Southshore.
Crushridge Warmonger: 0/15
Now that you've had a taste of the Crushridge ogres, I want you to really bloody their noses...
Go into the Ruins of Alterac and seek out the Crushridge Warmongers. I want you to cut down a good number of them - that's the only way those brutes will learn to keep their distance from Alliance territory.