Engetsu

Engetsu, written to mean Scathing Moon, is the sword of the veteran Shinigami Isshin Kurosaki. In its dormant state it passes for a plain tachi, sporting a red grip and a six-sided guard, and Isshin carries it slung on a cord around his belt in the iaidō manner, edge facing down and finished with a blue tassel at the pommel. Its power is rooted in fire.

The release word is 'Burn.' Calling it out leaves the blade's shape untouched but cloaks the edge in fire, which catches the tassels and drags them into long burning trails. From this state Isshin can spit his own blood onto the steel when injured, triggering an unnamed blast of flame fierce enough to sever an arm from the Hollow known as White. His signature strike is the Getsuga Tenshō, gathering spiritual energy in the sword before releasing it in a downward slash; in his prime he laced it with fire, and even after two decades without his powers the attack still flattened a full city block inside the fake Karakura Town and gouged a deep gash into Aizen's skull. Its Bankai has never been shown, said to strain the body so heavily that serious wounds make it impossible to summon.

Engetsu answers only to Isshin Kurosaki, its lone wielder.