Mōryōmaru

is a composite demon vessel created by Hakudōshi and used by the Infant to combat Naraku.

Overview
Mōryōmaru is one of Naraku's enemies. At first, he is merely a haku (life force) puppet, the more refined of various such creations made from yōkai by Hakudōshi. As such, he had no true personality, soul or will. After a couple brief altercations alongside Hakudōshi against Kōga and Inuyasha's group, he is given to Kanna, who places Akago inside of him (giving the puppet a soul). He is able to absorb the yōki that all yōkai possess and exert (making attacks based solely on yōki energy useless) and convert it into a powerful blast of energy which he releases from his arms (a technique he "lent" to Goryōmaru while he was attached to him, Chapters 356-366 in the manga). As far as personal essences go, he is actually Akago, the physical embodiment of Naraku's heart, and his yōki cannot be detected due to the Fuyōheki, a stone which completely masks the presence of any yōki near it. He has given a bit of trouble to Inuyasha and Sesshōmaru, since their attacks (the attacks from the Dragon-Scale Tessaiga and blasts from the Tōkijin respectively) are based on yōki, and therefore far from harming him, result in making Mōryōmaru even stronger. Through further modifications of his body, he seems to lose this ability or possibly because Sesshōmaru blew up the arm that had this ability. Kohaku eventually attempts to kill Mōryōmaru after Kagura tells him Mōryōmaru is after the shard of the Shikon no Tama in his back since his goal is Naraku's destruction, but fails, enabling Mōryōmaru to nearly steal the shard until Sango comes to his rescue. This in turn enables Mōryōmaru to flee from Inuyasha and company.

Increasing Powers
As the story progresses, Mōryōmaru begins to increase more and more in power as he absorbs different kinds of yōkai to gain their abilities. He seems to be more adept at this than even Naraku as he sends pieces of his flesh out to gather demon parts. Once he sent his hand to kill a bunch of male dragon humanoid demons and then absorb them, which Kōga witnessed. Here the main focus of the story begins to shift from finding and defeating Naraku, to stopping and destroying the growing Mōryōmaru. Mōryōmaru rarely appears before the group, instead he uses other powerful yōkai (whom he plans to devour later) he influences to fight them. But after he revives the corpse of Meiōjū (a turtle-like yōkai) and it regains its armored shell, Mōryōmaru manipulates the creature into battling Inuyasha and letting him strike it with his Kongōsōha (Diamond Spear Blast) attack. He then absorbs the Meiōjū and the diamond shards, incorporating them into his body and thus gaining a powerful armored shell of his own. The Kongōsōha are nowhere near as effective when used by Inuyasha due to the lack of the Kaze no Kizu. During the following battle, he nearly defeats an onslaught of most of Naraku's enemies which included Kikyō, Kohaku, Kagome, Inuyasha, Miroku, Sango, Shippō and even Sesshōmaru. During this battle he broke Sesshōmaru's sword, Tōkijin in the process. He only flees after nearly losing one of his shards of the Shikon no Tama. One might speculate that at this time Mōryōmaru had become even more powerful than Naraku as he was able to put up a fair fight against so many of his enemies which Naraku wasn't able to do even with the greatest portion of the Shikon no Tama in his possession. This difference in strength was also noted by Naraku himself in his conversation with Byakuya. Later, after Inuyasha gained the Senki, from a Nikosen, (for his Dragon-Scaled Tessaiga) Naraku sent Kanna to aid Mōryōmaru. He tried to absorb Ginka and Kinka, a pair of conjoined yōkai brothers (sharing an antagonistic relationship with each other not unlike that between Inuyasha and Sesshōmaru), as their blood would bond his armored shell together and prevent Inuyasha's sword from damaging it. Though he succeeds in devouring Ginka, Kinka allowed Inuyasha to absorb him with the Dragon-Scaled Tessaiga, thus giving him the "Flaming Tessaiga". The result is that when Inuyasha used Kinka's power against Mōryōmaru, Ginka's power struck back from within the shell. This greatly weakened Mōryōmaru, and he flees. Soon after, Miroku suggested that Mōryōmaru will discard Ginka's body (since it's become a weakness). In the anime, Mōryōmaru successfully absorbed Ginka and Kinka without any involvement with Kanna or Inuyasha's group, instead Bayakuya merely observes the fight and Sesshōmaru takes Inuyasha's place using the recently reforged Tenseiga.

Confrontation with Naraku
Sometime later, Mōryōmaru became involved in a plot by Naraku, and tried to steal Kōga's jewel shards for himself. However, he found himself at a disadvantage when Inuyasha and Kōga teamed up, with Inuyasha using the Dragon-Scaled Tessaiga's new technique to weaken Mōryōmaru, then Kōga using his Goraishi to break the surface of the armored shell. Even rearranging himself with the diamond spears wasn't enough to save him. Inuyasha broke through into Mōryōmaru's core and saw Akago. Before he could defeat the infant, Inuyasha was flung out when Mōryōmaru grabbed an extra jewel shard from Kai, a younger yōkai-wolf who was also caught up in Naraku's plan. With the shard in hand, Mōryōmaru escaped again, and reaffirmed his plan; to prove that he is superior to Naraku, just as Hakudōshi had intended to do until his death. A few days later, Mōryōmaru was seen to have regenerated, and escaped both Kōga and Kikyō, this time without fighting. Later in chapter 441 of the manga, Naraku ends up absorbing the power of the Yōmeiju, a yōkai-tree. Later he ends up running right into Mōryōmaru, who finished recovering from his fight with Inuyasha and Kōga. The jyaki, or evil energy, emanating from these two god-like beings was so strong that when they met the forest below them and all life in it was annihilated by a huge amount of miasma even though they were only headed for each other. Both exchange banter with Naraku saying that Mōryōmaru can't kill him as long as his heart is within Mōryōmaru, while Mōryōmaru says that Naraku can't kill him either for the same reason. Chapter 442 continues with Mōryōmaru continuously destroying Naraku's body with the Kongōsōha that he absorbed from Inuyasha, while Naraku tries to absorb Mōryōmaru back into his flesh and reclaim his heart. Since Naraku can break through Mōryōmaru's armored shell, he continues to cover Mōryōmaru's body. When it all seemed finished, Mōryōmaru's tentacles pierced the flesh and instead Naraku's (surprised) face and his flesh are seen absorbed into Mōryōmaru instead. The chapter ends with Mōryōmaru, unharmed, saying "Naraku, I am the victor!” while the members of Inuyasha's group look on in shock. Chapter 445 shows that Naraku is still intact within Mōryōmaru, much to Akago's shock. In chapter 446 he absorbs Mōryōmaru from the inside, thus leading to Mōryōmaru's eventual death.

Physical Abilities

 * Attacks using tentacles (later on uses tentacles covered in Kongōsōha spears for protection)
 * Has a right hand that acts as a gigantic tentacle made of Kongōsōha spears usually used to impale his opponents
 * He seems to be able make spear-like formations on almost any part of his body

Special Abilities

 * Live Body Pieces – Merging pieces of his flesh with other yōkai (and even humans such as Goryōmaru), thus giving him control over them and increasing their regenerative abilities. He often sends pieces of his flesh abroad to scout for new yōkai for him to add into his body.
 * Absorption – Absorbing yōkai and making his body stronger (Later on, he absorbs a yōkai named Meiōjū and gains a nearly impenetrable armor)
 * Yōki Absorption – Absorbing his opponent’s yōki (supernatural energy) and reflecting it back at them or simply consuming it to use as his own.
 * Raimeihō (Thunderclap Cannon) – Fires Black Balls of Lightning, this ability is gained due to the absorption of the Meiōjū.
 * Kongōsōha Spears – While both Inuyasha and Mōryōmaru possess this ability, the strength of this attack depends on the user’s yōki. Since Mōryōmaru doesn't have the Kaze no Kizu (Wound of the Wind) his attack can possibly be weaker than InuYasha's. This attack can possibly penetrate all barriers, as not a single barrier in the series has been able to withstand its force.
 * Shōki (poisonous miasma) + Kongōsōha Spears – After he absorbs Naraku, Mōryōmaru is able to upgrade his Kongōsōha attack by launching corrosive Kongōsōha spears infused with shoki. With the resulting damage increase, he was once able to melt entire mountains in one strike.

Trivia

 * In his original Haku form, Mōryōmaru's wings were peach/tan, now, they are bluish-purple.