Excuse me if its already known but when I was struggling with him(2nd Phase of course lol) and trying to learn his pattern there was a point where he smacked me to all the way to left side of screen. In my panic I jumped over that long range sword slash he sends and parried his close range slash. He then did that upward slash and I thought it was over for me but I saw it didnt touch me. Then he kept that same cycle as long as I didnt move from that spot. Jump over long range sword slash, parry, get some hits in while he cant touch you and repeat.

Of course this only lasted till halfway on his health bar until he changed to his last phase, but it did help me avoid most of the damage and save the Vials for this part of fight.

I had died multiple times before that and was wondering if this exploit was known(I can even try to get to that point again and record)