Speak to Darkrider Arly at Blackwatch in Icecrown.
The Scourge has a large facility called the Fleshwerks, dedicated to producing abominations and flesh giants. If we can shut it down, we can deprive the Lich King of a large component of his armies.
I've sent Darkrider Arly to the area. She has a small base, Blackwatch, on a ridge overlooking the Fleshwerks and to the west of Corp'rethar. I'm told the Argent Crusade is sending someone to coordinate their efforts there, but the darkrider will know what to do. Find and assist her.
Good. We'll need all the help we can get. Olakin here is the Argent Crusade's contribution to our effort. Let's cut the chatter and get down to the business of denying the Scourge their armies of the flesh.