Sekiro Shadows Die Twice: 10 Optional Bosses You Need To Fight

Honourable Mention: Great Serpent

Okay, so I'm cheating a little with this one, which is why it's been relegated to an honourable mention, because while you don't face off mano-a-mano with the Great Serpent, you absolutely need to find a way to take it out.

The primordial terror shows up a bunch of times throughout the game, forcing you to stealth around and escape its devastating jaws. Early on you have to stab the snake in the eye to progress, which send it into a fit of rage, but the boss comes back with a vengeance a few hours later.

Sadly, the way to actually kill the Great Serpent isn't obvious, and can be totally missed if you miss a certain side quest. I don't want to give it away fully - as discovering the opportunity awarded me with one of those "holy s**t" moments From games deliver so well - but you will need to solve a puzzle involving a kite first, and it's fully recommended you figure it out if you want to get the best ending.