Dakki

Dakki is a fantasy sword in the manga and anime of Inuyasha.

History
It was created by a sword-smith named Toshu, who wanted to create the strongest blade around. Through experimentation and creation of many blades, he found that blades of stronger yin yield better results. He started to collect broken swords from areas of confilct and despair. An act which soon earned the attention of the demon Ryujin, who was drawn to Toshu's yin and thus commissioned him (by Toshu's request) to create Dakki.

In the manga and the anime (Inuyasha the Final Act), InuYasha's group came to know about it after a fox demon, who tricked Shippo into helping him, fought with Inuyasha to steal the demonic energy with Dakki. However this version was not the true version, as it easily broke from a simple knock of Inuyasha's sword. They took a piece of the broken blade to Totosai, who examined it and told them about the sword-smith who forged it. When Inuyasha decided to find Dakki in order to upgrade Tessaiga, Totosai warned him not to be overconfident, as even the fake version was able to steal demonic energy quite easily, should Inuyasha have to battle the true Dakki, he could risked having Tessiaga devoid of its demonic energy and be in its battered form forever.

Later they rescued Toshu from Ryujin, who is angered that Toshu has not completed crafting Dakki. When Ryujin was defeated by Inuyasha with his Backlash Wave, Toshu used the sword to absorb Ryujin's power, thus completing Dakki and gaining the Dragon Scales, then battled Inuyasha and steal the demonic energy from Tessaiga. Through the course of the fight, Tessaiga began to have cracks on it as a result of its energy stolen, while Toshu began to turn into a demon himself. Soon Tessaiga turned back to its battered form due to the loss of energy, but not without finally making a small crack on Dakki. Despite the overwhelming sword skills of Toshu under the influence of Dakki, Inuyasha still battle him alone, as he believed it to be a fight between Dakki and Tessaiga, and he did not want to waste the opportunity provided by it to destroy Dakki.

Eventually Dakki, sensing the danger of getting destroyed, used the demonic energy taken from Tessaiga to kill Toshu, leaving behind only his hand attached to the hilt. Shortly after the blade broke from the crack, releasing all the stolen energy which returned to Tessaiga, followed by the ability to absorb demonic energy.

General Appearance
It takes the form of a regular katana which, after Toshu killed Ryujin and absorbing his powers, gains dragon scales on the backside of the blade. If a human were to wield the katana, the continuous absorption will corrupt that person, while changing him into a demon, with scales appearing on his hands (where they are gripping the hilt) and extending to his body.

Abilities
Yoki Absorption: It has the ability to absorb demonic energy from Demons and their attacks. The fake version was able to steal the demonic energy from Tessaiga from its attack, while the true version was able to steal large quantities by merely touching the Tessaiga.