This repeatable quest is given at the by Liege Aquila at the entrance of the Sprawl. It is one of several kill tasks that he will assign.
He will charge you to kill six Giantslayer Brutes, Bashers or Thugs (it's random each time you get the quest). These can be found in the Giantslayer area of the zone. They often come in groups so a group is helpful here.
The reward is experience and an iron ration.