The safest way to do this quest is to clear all the way to the Reaper of the Forgotten Vale (a short walk north of Mayor Alegheri) before taking any quests from the Reaper of the Labyrith. There should be a pair of Bladed Aatxes and three large groups of Grasping Darknesses along the way. There is also a group of Coldfire Nights and Stalking Nights that patrols near the statue of Grenth where the Reaper will appear.