Bakusaiga

Bakusaiga(爆砕牙 lit. Explosive Crushing Fang) is a sword from the manga series (Chapter 518 entitled "Bakusaiga") InuYasha that was created from Sesshomaru's own body. The Bakusaiga came from Sesshomaru's body attached to his finally regenerated arm. It is nearly unique in that it is one of two yokai swords in the InuYasha universe not forged from a yokai's fang. (The sword Sounga from the movie Swords of an Honorable Ruler was taken from the tail of a great demon killed by an ancient warrior, but did not manifest as a weapon to the living demon who spawned it - Bakusaiga is still unique in that respect.) It is Sesshomaru's final signature sword.

History
After shattering the Tokijin in combat with Mouryoumaru (Manga Chapter 407) and passing Tenseiga's only offensive technique Meidou Zangetsuha to InuYasha's Tetsusaiga (Manga Chapter 503) Sesshomaru is left without a fighting weapon beyond his own native abilities. While very few demons stand a realistic chance even against an unarmed Sesshomaru, the growing darkness in the Shikon no Tama allows a demon called Magatsuhi to escape from the jewel itself. Freed, Magatsuhi assembles a body from parts of Naraku and seeks out Sesshomaru in order to steal the last shard of the jewel from Kohaku, who is traveling with Sesshomaru. Sesshomaru accepts the challenge of battle but discovers Magatsuhi boasts a poison stronger than his own and sufficient strength to physically damage his remaining arm. The fight is interrupted by the arrival of InuYasha, who comes to his aid. Sesshomaru, angered by the implication of weakness inherent in the help and pity he receives from both his own followers and Inuyasha's group, manifests a powerful regenerative ability of his own and closes his wounds. The battle is again joined, and the use of Tenseiga against the otherworldly spirit of Magatsuhi offers hope of victory, but Sesshomaru is overmatched physically before he can deliver a fatal blow and is stabbed straight through his armor and chest by Magatsuhi, who contemptuously denounces his weakness. Before any aid can reach him, he is engulfed by a mass of demonic flesh controlled by Magatsuhi. InuYasha makes a desperate attempt to free him but only gets caught in the engulfing mass himself.

At this point, all parties are shocked to see the demonic mass blown apart by a massive burst of demonic power. The light is so blinding it takes several seconds for the group to see the light is in fact coming from the stump of Sesshomaru severed arm. Sesshomaru, angry and very much alive, drives back Magatsuhi's probes. At this moment the sword smith Totosai appears. Sesshomaru, seeing him and realizing in that instant what is happening, meets a massive thrust by Magatsuhi with an even more powerful wave of light - in that instant, within the light his arm regenerates and along with it a sword appears in the new hand.

Magatsuhi attempts to reassemble his body but discovers the hard way that pieces of his body attacked by the new sword transmit the blow they have received to undamaged parts - his body is destroyed attempting to reform.

In the course of the final stages of the battle Totosai reveals that the new sword is called Bakusaiga. It is not an heirloom or crafted sword but is created from Sesshomaru's own body as a manifestation of his own demonic power, and thus truly his own. His success in abandoning his interest in stealing Tetsuseiga as a quick path to power resulted in the development of his own inner strength, in the end surpassing even that of his father.

Sesshomaru uses Bakusaiga for the rest of the series to battle both Naraku and Magatsuhi. During the Final Battle against Naraku the Bakusaiga is used to destroy most of Naraku's body. In the final chapter set three years after Naraku's defeat the Bakusaiga is still carried by Sesshomaru.

Abilities
Decomposition: Bakusaiga appears to manifest a form of corrosive wave attack, an interesting manifestation of Sesshomaru's own power of corrosive poisoning as a sword attack. Miroku comments that Naraku would suffer the same affliction should he absorb any demon wounded by Bakusaiga. If there are any significant limits to the effects of the corrosive power they are not known - even the fully transformed body of Naraku was unable to stop or quench the effect and only avoided it by abandoning pieces to destruction. Only the Shikon no Tama itself withstood any Bakusaiga attack, and it appeared to be immune to essentially all demonic attacks of any nature.

Destructive Wave: The Bakusaiga's destructive wave is seen only once in the Manga, in Chapter 523 when Sesshomaru easily dispatches thousands of demons pitted against him to delay his arrival at another battle. If there is an upper limit to the strength of this wave it is not known.