Oh. My. God. This. Fucking. Guy.
This is the first boss of the DLC and it felt like the hardest boss by far. His attacks patterns are so brutal, you have have very little room for error because he can fucking wreck you so quick. If you manage to get hit once and not comboed, you still have very little room to heal, you basically have to wait for your next opportunity to dodge, and heal instead of getting a few hits in. In a way I think it's one of the best fights in the game because it really forces you to get good at memorising his attacks and the timing of them. Unfortunately he has a couple of moves (basically one in each form) that are effectively 1 hit kills. The one in his second form isn't so bad because it's easy to get out of the way of. The one in his first form, he jumps in the air, goes off screen for a couple of seconds and lands on top of you. I think I only managed to dodge it twice in all my attempts and of all the other times it hit me, it killed me in all but one. It just seemed incredibly random, I did the exact same thing the times I dodged it as all the times I didn't. It really cheapened a fight that was already extremely difficult and didn't need something like that. In my successful attempt the move never came out.
Watching a successful attempt doesn't really do the fight justice. You have to see (or experience for yourself) how quickly and easily this guy can kill you to understand. The first phase in particular of my video is really dirty - there were attempts where I played a lot better and dodged more of his attacks but then got killed by the cheap ass jump move. The second form though I do pretty well. His single sword slashes dont do a massive amount of damage when they his but there's one really fast combo that can kill if you get hit and staggered by the first swing. The 1 hit kill move in the second phase, he starts at 1:55. It looks like it's going to be the same move as the first time he plunges his sword into the ground but after the initial AoE he fires a continuous beam straight in front of him in a pretty large cone. If you get caught in that, you're dead.
The cool thing about this boss is you get that awesome sword at the end of it.