Soooo I'm playing more Skyrim and I'm at level 86, so basically it's not hard to kill anything. So I went to fight the ghost of Karstaag at the Castle Karstaag Ruins (you have to find his skull in the Glacial Cave first) over on Solstheim, and it was actually SUPER DIFFICULT. Not only is he a FROST GIANT ghost, and can therefore send me flying with a stomp of his foot, but he constantly casts Blizzard, so you never have any stamina and you keep get flung around because the space in which you fight him is so tight. It didn't help that I was using a bound sword (which did no damage btw) because I forgot to bring an actual sword, and getting close was difficult because of the stomping. The blizzard made it always difficult to see, AND he summoned ice wraiths, just to be annoying. I ended up having to use Fireball over and over (not to mention I used at least a dozen Ultimate Health and Ultimate Magicka potions) just to do any damage. It was seriously the hardest battle I've ever fought in that game (not including the Ebony Warrior, he's next).