TV-Series
Description
Magatsuhi is a central antagonist in InuYasha: The Final Act, representing the pure and concentrated evil of the Shikon Jewel. He is not a demon in the traditional sense but the very manifestation of the jewel's dark will, born from the souls of countless demons that were sealed within it by the ancient priestess Midoriko. For centuries, his spirit endlessly battled the jewel's good counterpart, Naohi, inside the sacred artifact.

Magatsuhi embodies evil in its most absolute form, arguably even more so than the series' primary villain, Naraku. Where Naraku possesses human emotions like jealousy, spite, and a desire for power rooted in his past as the human Onigumo, Magatsuhi is a purer, more primal darkness. He views all other beings as inferior, displaying a deep-seated arrogance and a sadistic pleasure in the suffering of others. He sneers at acts of courage and self-sacrifice, taunting his enemies as they risk their lives to protect one another. This immense pride and belief in his own invincibility ultimately contribute to his downfall.

Magatsuhi's primary motivation is to ensure the Shikon Jewel remains tainted and to eliminate any force that could purify it. He harbors a specific and intense fear of Kagome Higurashi's immense spiritual power, which has the potential to destroy him. From the moment she was born, with the jewel shard inside her body, he formed a connection to her and sealed away her true strength to prevent her from ever purifying him. He later allies with Naraku, who provides him with borrowed flesh to manifest a physical body in the world. In return, Magatsuhi works to defile the remaining pure shards of the jewel, particularly the one in Kohaku's back, and to assist Naraku in completing the corrupted jewel.

In the story, Magatsuhi serves as a formidable direct threat to the main characters. He is first given a temporary human-like form, a tall figure with long white hair and dark armor, constructed from Naraku's body parts. His first major act is to attack Sesshomaru's group to seize Kohaku's shard. During this battle, his true nature as a spirit of the jewel is revealed when Sesshomaru cuts him with Tenseiga, a sword that can harm beings from the afterlife. This confrontation is pivotal, as the desperate fight against Magatsuhi forces Sesshomaru to surpass his father's legacy, resulting in the regeneration of his left arm and the birth of his own devastating sword, Bakusaiga.

Key relationships define his role. He sees Naraku as a useful but inferior tool, considering himself far above the scheming half-demon. His contempt extends to Inuyasha, whom he mocks, and Sesshomaru, whom he repeatedly calls weak. He preys on the emotional bonds of his enemies, possessing Kohaku to torment Sango and later possessing Inuyasha to try and force him to kill Rin and Kagome, exploiting Sesshomaru's connection to the girl and Inuyasha's love for Kagome. His connection to Kagome is the most significant, as his existence is the direct cause of her sealed powers, and his defeat is what finally unleashes her full spiritual potential.

Magatsuhi undergoes minimal personal development, as he is a static embodiment of evil. However, his presence forces significant growth in others, most notably Sesshomaru. He is cunning and strategic, immediately recognizing advantages, such as using a hostage or hiding his essence inside a poisoned Miroku to escape certain death. His notable abilities are rooted in his non-corporeal nature, making him immune to most physical attacks. He can only be harmed by spiritual or holy weapons like Tenseiga. He possesses immense demonic power, capable of corrupting jewel shards with a touch and producing a miasma potent enough to injure even Sesshomaru. His most dangerous skill is possession, allowing him to take control of others and torment them from within. Ultimately, he is destroyed when Sesshomaru uses Tenseiga to banish his spirit from Inuyasha's body, an act that simultaneously breaks the seal on Kagome's spiritual power.