Tenken is the manifested spirit of Sajin Komamura's Zanpakutō. He appears during the anime-exclusive Zanpakutō Rebellion arc and the Tōjū Campaign that follows.
Despite looking imposing and powerful, Tenken is surprisingly composed—he's never been shown losing his temper. Gonryōmaru claims he's actually quite shy, much like Komamura himself, which apparently explains why he barely speaks. In fact, he's only uttered a single word on screen: "Bankai," delivered in a deep, resonant voice.
Content compiled by AnimeList.moe from publicly available sources.