Mukai Kaku (S03E01)

The mad monk Lóu Zhèn Jiè and his sword, Seven Blasphemous Deaths, were defeated and cast over the edge of a cliff in the Demon Spine Mountains... but only a fool would allow such a powerful demonic sword to lie at the bottom of a ravine, where it could pose a threat again in time. Shāng Bú Huàn and his allies search the dark mountains depths for any traces of their enemies, unknown that an alliance to destroy them is forming in the shadows. (Crunchyroll)