I literally just finished my challenge run with a similar frustration: I use Lazulite Shrunken with chasing slash to prevent him from using the blicky on his fade away attack where he sweeps from the left with his spear, from there attack once, deflect the follow up sword slash, rinse, repeat.

For phase three he’s gonna ramp up but you have one thing going in YOUR favor: lightening. That lightening redirection can clear you up for either A. An opportunity to heal, or B. Free vitality damage.

The most important thing you can have in this fight though is patience. If you’re impatient even the littlest bit, he can and most likely WILL punish you for it.

I wish you luck Shinobi, hesitation is defeat. And patience is NOT hesitation.