I've been trying for this quest for quite some time and haven't gotten a single helpful answer. Most people just say oh you gotta do the quest line, but that's all they say. I am assuming it's just bugged and can't be done on xbox currently. Since I have done the coop version off Illezra's Threat but can't proc the normal one. Some of the pre quests don't actually exist and some are renamed. So could be an oversight and it wasn't added, or it's a bug is my guess.