Zabimaru

At rest, Zabimaru passes for an ordinary katana, distinguished by a jagged bronze guard and a matching red grip and scabbard. Its Shikai stretches the weapon into a chain of six ridged segments, each broader than the last, studded front and back with pick-like fangs and joined by an elastic cord so the whole thing lashes out like a whip yet still cuts like a sword.

When Renji reaches the true Bankai, Sōō Zabimaru, a snake-skull gauntlet ringed in red fur locks onto his right arm, trailing a long spine of vertebrae that hangs at his waist, while a green-furred mantle and armored collar drape his left shoulder. A blade slides from the serpent's jaws to give this form the edge its predecessor lacked.

In Shikai the sword hides a seldom-used trick called Higa Zekkō, in which Renji suspends its scattered segments in the air and rains them down in an all-directional strike, a gamble that spends the whole weapon and leaves him briefly unarmed.

The true Bankai unlocks a far wider repertoire. Hihiō turns the fur mantle into a giant skeletal arm that crushes bone and hurls foes, jet-boosted by flame; Orochiō unfurls the tail into a serrated blade hot enough to melt stone. Renji can seal an impaled enemy inside jaws of spiritual energy and fire straight through them with Zaga Teppō, whip the blade into a segmented lash via Zazekka, pin opponents beneath conjured skeletal hands using Hihi Tenshō, or charge a spinning disc of energy for the cratering Zagai Zekkō. The old standby Hikotsu Taihō, a concentrated cannon blast, carries over from his earlier Bankai.

For much of Renji's career the blade withheld its real potential. Because its spirit only half-trusted him, it handed over a bogus Bankai title, leaving him to fight with an incomplete release called Hihiō Zabimaru, a colossal serpent of bone whose segments Renji could detach and rebuild at will through sheer spiritual power. Renji himself rated it the most demanding of any lieutenant's Zanpakutō to control, thanks to the whip-and-sword duality of its Shikai.

Only after Ichibe'e Hyōsube spoke its genuine name and Renji proved his worth to the spirit did the weapon abandon that limited form and grant him the real Bankai, Sōō Zabimaru. Its sealed shape had earlier been broken during Renji's duel with Ichigo Kurosaki.