Kagetane

Kagetane (影胤, Shadow's Offspring) is a Zanpakutō who was detached from his owner through an occult, Kidō ritual two centuries ago. Due to the nature of his separation being foreign to that of 's ability, he retains his sentience as a Zanpakutō Spirit, and doesn't possess any inherently berserk actions or negative emotions towards the Gotei 13 at large. However, he appears to be particularly scornful of his owner, considering his mistreatment of him. Within Bankai, Kagetane is known as Kagetane Hiruko (影胤蛭子, Shadow's Offspring, Leeching Child), indicating that his master was a sufficiently powerful Shinigami.