Tenseiga

The Tenseiga (天生牙) is a fantasy sword from the anime and manga series InuYasha.

The sword has a special property in that it cannot harm any living beings, which is ironic for a sword. However its power lies in the fact that it can bring the recently dead back to life as well as healing the wounded. The literal translation of the kanji is "heavenly life fang" or "fang born out of heaven", but these are not necessarily accurate representations of the name's actual meaning.

Tenseiga allows a powerful wielder to see and slay the beings from the underworld, as well as bringing up to 100 beings back to life in one swing.

It is wielded by the yōkai Sesshōmaru. The swordsmith Totosai created it along with the Tessaiga from the fangs of Sesshomaru's father, who was a taiyōkai(literally great yōkai) dog demon famous throughout the lands.

Tenseiga has been used sparingly, mostly only when Sesshomaru feels like using its power for his own gains such as reviving the head of the yōkai Goshinki so that his fangs can be used to create the sword Tokijin; or when the sword compels Sesshomaru to use him for a good cause. Sesshomaru does not fully understand the behavior of the sword but he keeps it by his side for it almost always has some unforseen benefit.

Sesshomaru's human campanion, a human girl named Rin, is brought back to life with the Tenseiga after she was killed by the demon wolves of Kōga; Jaken, Sesshomaru's assistant, is also revived by Tenseiga as well after Kaijinbo kills him while under the corruption of the Tokijin.

Tenseiga, interestingly, easily defeats the leader of the elite cats of the west, Oyakata, who becomes an undead when he is revived with the souls of his lieutenants who laboured to complete the task and 3 pieces of the Shikon Jewel. Using the sword, Sesshomaru restored the life back to the lesser cats, thus taking Oyakata's life essense away. InuYasha is then able to finish the job with the Tessaiga and put an end to the renewed war between the Cats and the Dogs.

Since Tenseiga can harm the beings of the netherworld, the guardians at the gate that seperates the Living World and the Dead, Gozu and Mezu, will not attack anyone who wields the Tenseiga, thus allowing them to pass the gate unobstructed.

However, Tenseiga is not all-powerful as appearantly it is not able to save Kagura, the wind sorceress created from Naraku and wind. The sword is either unable or unwilling to help such beings that do not possess a soul to being with.

In the third theatrical release of the InuYasha series, it is shown that when InuYasha and Sesshomaru's father was yet alive, he saved InuYasha's mother Izayoi and baby InuYasha with the Tenseiga. Subsequently, as the events develope, Tenseiga and Tessaiga, and in turn Sesshomaru and InuYasha, combine their power to utterly destroy Sō'unga, the sword of world conquest, which is more powerful than either of the other two swords alone and has a mind of its own that is bent on destruction.