Just defeated The Broken vessel and figured I’d share what I did since I had such a hard time

I used the Stalwart Shell, Shaman Stone and Steady Body charms.

I hit the boss 13 times to stagger it with the nail (1x upgraded nail) then used the Desolate Dive every time it did its projectile downward slash and timed my hits for after each dash and attack.

When it is staggered, heal, and use the ghosts to get soul if you’re running low.