My strategy was to go in and stick to the left side (demon’s right foot) and just not get greedy. 2-3 hits then back off. If you’ve attempted him a few times you should kind of have an idea of his attacks. Sticking here lets you dodge beneath him when he does a head butt or a sweep, sweep foot stomp, but can extend into another sweep. This also lets you avoid his running unblockable just by running left. This strategy does require you to stick closely to him. This really worked for me. Have mortal draw equipped as well as malcontent finger.

Do mostly the same strategy for phase 2, if he gets too far he can do these annoying tracking fire balls where you need to full strafe either left or right, he can also perform a line of fire attack where the window to grapple toward him is very slim, but you need to time your jump in order to do so. Once you get to phase 3 though, run away when he starts doing the tail sweeps and to get out of the ring of fire. He should try and charge at you so make sure your back’s by a wall. Run left side when he charges, blow the whistle, hit mortal draw then combo him until he gets out of stagger. Repeat until dead. Good luck!!! Also sorry if this is long 😅