Guardian Ape

About

He's found deep within the Sunken Valley. In a shallow pond overlooked by a giant statue, this lonely and immortal beast protects the Lotus of the Palace. As the flower's aroma attracts female apes, he carefully tends to it, hoping to offer it her new mate.

The Ape also has a connection to the Sculptor from the latter's younger days when he trained in the Sunken Valley. His partner, Kingfisher, had a finger with numerous holes bored into it that could create a howling whistle when blown into. When the Guardian Ape is defeated, Wolf receives the Slender Finger, which the Sculptor recognizes as that of his friend's. This implies that the woman ended up devoured by the beast after a fight, possibly scarring his body and leaving her sword in his neck.

(Source: Sekiro: Shadows Die Twice Wiki)