The quest Starting The Negotiations requires killing the same mobs, so it is strongly recommended that you do both quests at the same time. This may require some coordination to get both quest lines to the same point.
Slay the following dervishes (level 14-16). They are found at two particular places in The Dervish Encampment ( 1100, 0, 200 ) /waypoint 1100, 0, 200. You may have to clear the camps a few times to get the types that you need to spawn.