Naraku's barrier

Naraku's Barrier (奈落の結界, Naraku no Kekkai) was a protective shield used by the main antagonist of the series, Naraku. He used this barrier to hide and protect himself from the attacks and advances of his enemies. Some of his incarnations, such as the Infant, Hakudōshi and Byakuya, also employed this barrier, as they were "born" after its creation. Naraku's incarnations "born" before the creation of the barrier, such as Kagura and Kanna, were not able to employ it.

Synopsis
There were a total of three types of barriers created by Naraku; one used for hiding, and two others to defend himself and repel attacks. Naraku and his incarnations' use of these barriers became a crucial part of his strategy, especially after the creation of the last barrier that proved to be a major obstacle for Inuyasha, Sesshōmaru and Kōga. However, none of these barriers proved to be completely invulnerable, as the protagonists found new methods to break through them as time went on.

Castle Barrier
Initially, Naraku employed a large barrier that completely covers his castle. The purpose of this barrier was not to protect against attacks, but instead to hide his demonic aura, his scent, and the presence of the shards of the Shikon no Tama he had collected. Being a half-demon, there was a day each month where Naraku would lose all of his demon powers; however, in contrast to Inuyasha, he could choose when this transformation occurred, and take advantage of this opportunity to recreate his body, discarding the unnecessary parts. This transformation also diminished the strength of his barrier, allowing Kagura to leave the castle, and allowing Kōga and Inuyasha to sense Naraku's jaki and smell.

This barrier is used for the last time in the clash at the castle against Sesshōmaru and Inuyasha. However, towards the end of the manga, when Naraku takes Kagome Higurashi hostage in order to obtain the last shard of the Sacred Jewel, he hides himself behind a barrier (at this time, Kagome's powers were sealed by Magatsuhi).


 * This barrier is large, and thus may house other beings as well as Naraku.
 * It can be easily broken by Inuyasha's Red Tessaiga, as shown in the clash at the castle with Sesshōmaru before Naraku's temporary disappearance.
 * It is not known if this barrier could withstand more powerful attacks.

Protective Barrier
Naraku's second barrier, in contrast to the castle barrier, was designed to deflect the attacks of his enemies. In the clash with Muso (Onigumo), after reabsorbing him, Naraku is attacked by Inuyasha with the Kaze no Kizu, but his barrier is totally immune to the attack, seeming unbreakable. This prompts Inuyasha to search for a way to break through all barriers; this quest ultimately ends with Inuyasha obtaining the Red Tessaiga.

Kagura kidnaps Rin, and Naraku decreases the power of his castle barrier, attracting Sesshōmaru in order to absorb his body and demonic energy. After Naraku employs his protective barrier as protection against the Kaze no Kizu, Inuyasha unleashes his Red Tessaiga and destroys it.

After the clash at the castle, Naraku never again employed this barrier, instead employing his next, more powerful barrier.


 * This barrier was able to endure powerful attacks, even Tessaiga's Kaze no Kizu.
 * It was much smaller than the castle barrier, but it still may house other beings as well as Naraku.
 * It could be destroyed by the Red Tessaiga.

Upgraded Protective Barrier
Naraku employed his third and final barrier for the first time at Mount Hakurei, using the powers of the Sacred Jewel shards in his possession, along with his newly reformed body. Inuyasha's group clashed with Naraku inside the mountain where, once his body was put together again, he employed the new barrier. In the anime, Inuyasha hit him first with the Sankon Tessō (or "Iron Reaver, Soul Stealer" in the English dub) without success, then tried again with Tessaiga's Kaze no Kizu, but the new barrier proved to be much stronger than the previous one. In addition, this barrier obtained the power of being able to turn the energy of an enemy's attack back to them. Naraku used this ability first against Inuyasha, turning the Kaze no Kizu against his group, and then against Sesshōmaru, who was waiting for him outside Mount Hakurei. Sesshōmaru, however, was able to overcome the kenatsu energy of Tōkijin and launch a new attack against Naraku.

This barrier's power could also be used by all of the incarnations Naraku created after his "rebirth" at Mount Hakurei, namely the Infant, Hakudōshi, and Byakuya, though Byakuya only demonstrates that ability in the manga.

In the clash with Hakudōshi, it was shown that even Red Tessaiga's power has no effect on this new barrier. However, this barrier was not indestructible; in the same battle, Kikyō brought it down with one of her sacred arrows, which was combined with soil from Onigumo's cave. The soil was infused with the passion Onigumo felt for Kikyō, which Kikyō later discovered could work to undermine Naraku's power and aggression towards her.

During the battle in the Inu no Taishō's tomb, when Inuyasha and his group faced Naraku, Kagome's purifying arrows, Tessaiga's Bakuryūha, and Sesshōmaru's Tōkijin prove ineffective against Naraku's barrier. Only the diamond spears of the great demon Hōsenki were able to pass through the barrier and harm Naraku's body directly. This ability was later voluntarily transferred to Tessaiga by Hōsenki, and Inuyasha used it to launch a decisive blow against Naraku, causing great damage to his current body with some contribution from Sesshōmaru and Kikyō's arrow shot by Kagome, which was also treated with soil from Onigumo's cave.

The combined powers of the demon brothers Ginka and Kinka also proved effective against the barrier when they face off with Mōryōmaru in the manga. The lightning and the fire they produced passed to the insides of Mōryōmaru's body, using his tentacles as a conduit when he was trying to absorb them, and eventually they managing to bring down the barrier that the Infant constructed around himself. Mōryōmaru did manage to absorb one of the brothers, Ginka. However, Mōryōmaru was forced to give up on him as even inside his body, Ginka's power was resonating with Kinka's flames, and since Kinka was absorbed by Tessaiga, there was a danger that every time Tessaiga used its flaming powers on Mōryōmaru, the barrier shielding the Infant inside him would be brought down.

A third demon was shown to have the power to pass through Naraku's barrier: the demon tree Yōmeiju. This creature fed on both humans and demons, and for this purpose it had developed tendrils that had the ability to break demonic barriers. It was shown tying Naraku up through his barrier, though Naraku turned the table on the demon tree and absorbed it just as it was preparing to devour him. He did this in order to dissolve the Infant's barrier and reclaim his heart. Naraku succeeded in his plan, absorbing both the Infant and Mōryōmaru.

Just as Naraku was done absorbing Mōryōmaru, Kōga, who was located inside his body, tried to attack the Infant (Naraku's heart). Though Kōga was in danger of being dissolved by Naraku's shōki, he was protected by the spirits of his wolf demon ancestors, who received help from Kagome's arrow. He uses the Goraishi against the Infant; however, the Infant was still inside the barrier, and Kōga's attack was not successful.

When Hiraikotsu was reforged for Sango thanks to the demon sage Yakurōdokusen, her weapon gained the ability to pass through demonic energy, as well as barriers. This was also shown in the final battle, where Sango's weapon passed through Naraku's barrier, causing great damage to his body. In the same battle, the barrier proved ineffective against Kagome's sacred arrow, thanks to a teleporting technique she learned from the battle against a powerful priestess named Hitomiko, whose body was manipulated by Naraku after her death. The technique allowed Kagome to hit her target even when the target was behind a solid object, making the barrier useless against Inuyasha's crew. By the time of the last battle, Inuyasha could also break Naraku's barrier with the Kongōsōha and cast Naraku into hell with the Meidō Zangetsuha together with the barrier (though it should be noted that Naraku was protected several times from this technique by the Jewel's own insistence on clinging to this world, using Naraku's body as its instrument). After Naraku used the power of the Jewel to reach his final form, the barrier no longer appears, a sign that it was no longer useful.


 * This barrier was in the shape of an oval, slightly smaller than Naraku's previous barrier.
 * As with Naraku's other barriers, it could house Naraku and other beings.
 * The owner of the barrier could cross it from the inside, but others could not (as with Kagura).
 * It was immune to frontal attacks such as Inuyasha's Sankon Tessō, Kaze no Kizu, Red Tessaiga, and Bakuryūha, Sesshōmaru's Tōkijin, Sango's Hiraikotsu (before being reforged), Kagome and Kikyō's normal sacred arrows, Princess Abi's flames, Kagura's Wind Blades, Kōga's attacks (including Goraishi), the attacks of Goryōmaru's goryo urns, and many others.
 * It could be damaged by the combined attacks of Kinka and Ginka, as well as the Dragon-Scaled Tessaiga, among others.
 * It could be destroyed or passed through by the adamant spears of Hōsenki/Inuyasha's Kongōsōha, by an arrow imbued with soil from Onigumo's cave shot by Kikyō or Kagome, from the branches of Yomeiju, by an arrow shot by Kagame using Hitomiko's method, and Sango's reforged Hiraikotsu.
 * It is unknown if it was able to resist the attack of Bakusaiga, Sesshōmaru's new sword.
 * In the last season of the anime (The Final Act), when Naraku kidnapped Kagome, Inuyasha inexplicably destroyed Naraku's barrier using the Red Tessaiga, which was not feasible, since this power had no effect on Naraku's previous barrier.  This was probably an oversight of the producers of the anime, since the scene was different in the manga; instead, Inuyasha did not use the Red Tessaiga, and Naraku instead removed his barrier to show his enemies that they could not hit the Jewel, as it was protected by the armor of Meiōjū.

Naraku & Hakudōshi
Naraku and Hakudōshi are connected through their barrier, a benefit that Naraku employed several times. On two occasions, Naraku used this connection to "teleport" into Hakudōshi's barrier, first in the Inu no Taishō's tomb, second in the Rock Ogre's stomach, where Naraku trapped his enemies.

Naraku used this connection for the last time to get rid of Hakudōshi, who, along with Kagura and Mōryōmaru (with the Infant), had tried to betray him. Naraku removed Hakudōshi's barrier and disbanded the Saimyōshō, allowing Miroku to suck Hakudōshi into his Kazaana.