Grandmaster Delve sucked to solo, but I took my time and scraped by. But if you think Delve was the hardest thing ever, you'll find Grandmaster Fikrul's Castle the most masochistic thing ever. It's a different animal from Delve. It's worse than the Ultimate Conquests. It's the Conquest that Fireteam Finder players regularly ragequit. It was miserable and stressful to do, and the time I wasted trying to solo it was maddening. And this was after 2 practice runs on normal difficulty. Yeah, the later Conquests are frustrating. They need a difficulty tweak.