Approximately every fifteen minutes there will be a group of three Kolaz Umgal Runebrand dwarves that walk by this location one after the other. They stop and group up and then Haaloth Bloodreaver will come out to rob and kill them. Allow Haaloth to kill all three and then kill Haaloth to recieve the unlock.
Note: it is hard to solo this mob, so you should bring along some friends to kill him :)
This NPC also drops level 30-35 purple and blue items, one of which is prized by Order being that they can be used as a skin for the shield for a tank that shows as an Orc shield. All items are bind on equip.