Blackhat Badger's Questline

Blackhat Badger is a merchant found in Ashina Castle, near the Old Grave Idol. He sells the Anti-air Deathblow text. After the castle is invaded, he moves to the Senpou Temple, Mt. Kongo - Temple Grounds Idol. He'll ask you to retrieve a 'bell' from the Great Serpent Shrine. This leads to an encounter with the Great Serpent. After this, he moves to the Dilapidated Temple. His quest is short but provides access to a useful combat art and some unique items.