Hi I don't have access to elite so if this is in there, I'm sorry.
Start up the quest mentioned and go to the old ruins. go to the left. you'll go through a path and see a house with a cellar. if the door is no open. leave and resume. but if it is open go inside. you'll see a purple name mob and 4 followers. For me I can cast on them and they won't attack me as long as i stand in the doorway. It drops a bunch of stuff each time. If people need helping finding it I can post a picture. also i believe the door is called dark cellar. I did not find this out but I noticed it wasn't on here.
edit: i forgot to mention that after u get the loot, leave and resume