Magatsuhi

is the yōkai who killed Midoriko and whose soul with whom she continuously battles inside the Shikon Jewel. Magatsuhi was created by numerous demons who formed into one demon in order to kill Midoriko. Magatsuhi's true form is much more monstrous.

During the story
Magatsuhi is first seen in manga chapter 89 as the mummified corpse of an unnamed but massive demon. He is the demon who fought and died with the ancient priestess Midoriko hundreds of years ago.

Later in the manga, the demon's name is revealed to be Magatsuhi, and Naraku helps him manifest in physical form so that Magatsuhi can help him complete the Shikon Jewel. Magatsuhi seems to fear Kagome's spiritual power and seals away her true strengths to prevent her from purifying him. Magatsuhi's first mission after coming to life is to defile and obtain Kohaku's shard but he is obstructed by Sesshōmaru, whose sword Magatsuhi fears, as it can kill him. Magatsuhi flees after being injured in the fight (having lost the flesh Naraku lent him), and along with Naraku tricks Sesshōmaru into leaving Kohaku alone with a fake Magatsuhi.

He succeeds in kidnapping Kohaku, made unconscious by Magatsuhi's defilement of his shard, and severely injures Sango and Miroku who tried to stop the demon. He remained in control of Kohaku, tormenting the boy with visions of his past, until Kohaku managed to awaken and break free of Magatsuhi. Kohaku then attempted to drive the demon from his body, even at the cost of his own life. Magatushi curses him and fights back until being slashed by Sesshōmaru, who has returned after realizing he was tricked. Sesshōmaru attempts to kill Magatsuhi but he escapes at the last moment, having hidden his essence in Miroku, who he poisoned.

Magatsuhi then appears inside Naraku's enormous body in the final battle, possessing Inuyasha and trying to kill Rin and Kagome. Sesshōmaru mocks him, taunting Inuyasha was the worst person to possess and Magatsuhi finds Inuyasha fighting back at his control. He is driven from Inuyasha's body and after trying to take over Kagome, is killed by Sesshōmaru.

In chapter 555 in the manga, Magatsuhi's spirit is combating Midoriko inside the Sacred Jewel. However, he is split into the many demons that formed him. Magatsuhi states that if Kagome were to make a selfish wish on the Shikon Jewel, Kagome would replace Midoriko in the eternal fight in the Jewel and Naraku would replace him.

Inuyasha refuses to believe Magatsuhi, and proceeds to attack it in an attempt to reach Kagome and save her. In the end he and Naraku were destroyed forever by Inuyasha when he cuts the point of light in the darkness inside the Shikon Jewel with the Meidō Zangetsuha and arrives in the Meidō outside the Jewel to save Kagome. Then Kagome makes the right wish; the wish being for the Jewel to be taken out of existence. The Jewel breaks and then disappears, and Inuyasha and Kagome are transported back to earthen ground.

Physical description
While he is an amalgamation of demons residing in the Shikon Jewel, his incorporeal form is that of a disembodied pale face with red eyes and sclera and blue stripes on his cheeks. When he manifested in the living world through Naraku's flesh, he assumed the form of an adult male with long, shaggy white hair similar to Inuyasha's, smaller facial markings, blue lips and wore a set of dark armor. His arms were of a pale purple colored and most of the time, were a set of three sharp tendrils. As the body did not truly belong to him, he could deconstruct it back into the parts he borrowed form Naraku, keeping only the head in its form so he can speak.

Personality
As the embodiment of darkness of the Shikon Jewel, Magatsuhi is pure evil, perhaps even more so than Naraku himself. He views every other single being, living or not, as inferior to him, repeatedly calling Sesshōmaru weak and disliking any comparisons of him to Naraku. He sneers at courage and self-sacrifice as seen when badly injuring Miroku and Sango, taunting Miroku for absorbing Magatushi's deathly poison to save Kohaku from him and sneering that he will die. He also is sadistic, promising Sango he will return her brother as a corpse once he is through with him. However, like traditional villains, his arrogance makes him underestimate his opponents which usually costs him to lose a battle.

Powers & Abilities

 * Immense Demonic Power: Representing the evil of the Shikon Jewel, Magatsuhi is terribly powerful, having backed both Inuyasha and Sesshōmaru in demon form into a corner. His power appears to exceed even Naraku's, calling himself a league far beyond his.


 * Shapeshifting: Magatsuhi has the ability to transform a part or his entire body into a plethora of large, thick tentacles capable of deadly constriction as well as used for impaling enemies. Magatsuhi has no definite form. Like Naraku, he, too, is an an amalgamation of demons, briefly borrowing flesh from Naraku to assume a physical form in the material world.


 * Immortality: Magatsuhi shows incredible resilience on the battlefield, shrugging off a decapitation as if it was nothing and in his spirit form, is immune to all forms of physical combat.


 * Corruption: Magatsuhi's darkness is so vast and dense that a simple stare corrupted and temporarily knocked out Kagome.
 * Possession: Magatsuhi can possess another's body. He did this to Rin, Inuyasha and Kohaku.
 * Miasma: Magatsuhi's miasma is one of the strongest if not the strongest in the entire series. His miasma is strong enough to seriously injure Sesshōmaru who is very much immune to poison and is of course fatal to humans. His miasma almost kills the monk Miroku who, if not for Magatsuhi fleeing from Sesshōmaru through Miroku, would have certainly died.

Quotes

 * "You are weak, demon."
 * "As long the Tainted Piece of Shikon no Tama existed, my power is limitless"
 * "Stupid woman, you still didn't realize that your spiritual power is sealed within me."
 * "It is useless, I won't let you go to her."