Hyourinmaru

Hyōrinmaru ("Ice Ring") When sealed, Hyōrinmaru looks like a normal katana with the exception of the guard, which is in the shape of a four-pointed bronze-colored star. Its hilt is light blue and sheath dark blue. The sheath completely dissolves when he draws his sword. The sword is somewhat longer than most Zanpakutō, at about 1.4 meters long, making it taller than Hitsugaya, preventing him from wearing it at the hip. Instead he carries it on his back by his green sash over his right shoulder. Hitsugaya is one of four people that carry a Zanpakutō on their back, the others being Ichigo Kurosaki, Love Aikawa, and Hiyori Sarugaki.

Hyōrinmaru is the strongest of all ice-element Zanpakutō in Soul Society. As such, Hitsugaya doesn't need water to be present in order for him to use its abilities. Hitsugaya's control over Hyōrinmaru's power has been shown great enough to use any of its Bankai attacks (with less control) with Shikai

The spirit of Hyōrinmaru is that of a gigantic, ice blue, serpentine ice dragon with large wings and an echoing voice. Hitsugaya has had a close connection to his blade since first awakening his Shinigami powers. Before Tōshirō began training to control his Shinigami powers and leaking reiatsu, Hyōrinmaru would constantly appear in his dreams in an icy landscape (most likely Tōshirō's inner world) and call out to him, although Tōshirō was still not able to hear him. Hitsugaya inner world is seen as an icy landscape easily accessible to him as he enters into a meditative state.