The third boss Nioh 2 is a fat, naked, serpentine Yatsu-no-kami, and it's no child's play. You want to take your time with this boss because he has a large sword-shaped horn attached to his face and two serpent heads that act as arms on either side of his body. Once you understand Yatsu's patterns, you should have no problem removing him.
When the fight begins, the snake will dive straight towards you, forcing you to dodge left or right. The direction doesn't matter as long as you dodge. Immediately after that you can dive straight into it to deal damage, but you want to get away from there and wait for it to attack. Yatsu-no-Kami works a little differently from other boss fights, where you want to wait for him to attack to line up the correct counterattack.
For example, when he places the two serpent heads on the ground, they will rise up under you, so you want to rush straight at Yatsu-no-Kami during this time, so when the attack ends, you're next to it and you can deal quick damage. After that, roll over and wait for another opening.
Yatsu-no-Kami has the snakehead attack and continues to dive through the arena to attack you every now and then. You can counter this, but it's pretty quick and infrequent. You want to avoid attacking him directly to avoid getting caught by this attack, so come at an angle. Additionally, it will summon a series of translucent projectiles that traverse the battlefield. If you can see when Yatsu summons them, these attacks are easy to dodge. It uses projectile attack in the normal and dark range.
When it enters the Dark Realm, the serpent heads break free from its sides and become different snakes that shoot poison at you. These two move freely from Yatsu, so you want to keep your eyes on them. In addition, by removing them, you can return to the normal realm. Defeating them is your priority the first time you travel to the Dark Realm. If you dodge the Yatsu you should be fine, but he will try to grab you and deal big damage to you with tail swings. The grapple appears as Yatsu is trying to wrap itself around you.
Yatsu will continue to follow the pattern of these attacks during your encounter. Once you're closer to the end of the fight and Yatsu has less health, you want to focus on attacking the Dark Realm rather than the little snakes. There's a lot of reps during this boss fight with not too many special mechanics to think about. You definitely want to bring an antidote with you, to combat any poison you may get from the little snakes.
