This is first part of the orc saga running in Redridge Mountains. To begin it, speak to Marshal Marris near the bridge. He will say:

The Blackrock orcs have travelled from the Burning Steppes and claimed Stonewatch Keep to the north. From there they maraud the areas north of Lakeshire and keep its citizens in town, penned like cattle.

Help rid Lakeshire of this menace. Kill these Blackrock orcs and bring me ten of their Battleworn Axes as proof.

And although Blackrocks threaten us from the north, we've received reports of more in the southeastern pocket of Redridge. If you find any there, then they too should be hunted.

Collect 10 Battleworn Axes
Return to Marshal Marris

Some characters might be able to solo this one, but in most cases it's necessary with a small group. You will find the Blackrock Grunts (level 19-20) and Blackrock Outrunners (level 20-21) just north of Lakeshire, lurking in small groups behind trees and rocks. They attack with nets that root you to the ground, and they like to attack in small groups of 2-3 as well, so be very careful. Once you have the axes, return to Marshal Marris who will say:

That makes for a lot fewer orc warriors to worry about, thanks.

Completing this quest will begin another one called Tharil'Zun.