Tessaiga's sheath

, also spelled Tetsusaiga's Sheathe, is a scabbard powerful enough to contain the powers of the Tessaiga itself. As such, it is capable of projecting barriers, which Inuyasha uses on multiple occasions to save his life.

History
It was made by Tōtōsai from the donated boughs of the mystical demon tree yōkai Bokusenō.

During the Story
Inuyasha first used his sheath during a battle against the Thunder Brothers. It protected him against many of the vengeful Hiten's lightning-based attacks while Tessaiga was out of his reach. However, multiple attacks caused it to crack from the barrage of white electrical thunderbolts.

After the battle against the Thunder Brothers, Myōga directed Inuyasha to leave the sword and sheath by a nest of steel wasps, explaining that the wax produced by the yōkai insects would repair the damage the sheath had sustained.

Inuyasha used the sheath to protect himself from Sesshōmaru when he stole Tessaiga from him.

Inuyasha used the sheath to protect himself from one of Ryūkotsusei's energy orb attacks while he was attempting to pick up the Tessaiga while still under the rogue influence of his demonic self. However, the sheath was noted to be at its' limit after protecting Inuyasha once.

When Inuyasha was trapped inside Tōkajin's gourd, he used the sheath to guide Tessaiga towards the gourd so it would create an opening large enough for him to escape (he was devoured by Tōkajin in the manga and used the sheath to draw in Tessaiga to hit his stomach and cause him to regurgitate Inuyasha).

During their final showdown with Naraku, Inuyasha had created the demonic shield to protect himself, Kagome, Shippō and Miroku from the very large and powerful tornadoes of miasma that swarmed around them, which were far more effective.

Hanyō no Yashahime
Eighteen years since the death of Naraku and destruction of the Shikon Jewel, the two thousand-and-eighteen-year-old Bokusenō had informed Moroha that his very own boughs had fashioned Tessaiga's sheath as well as that of Tenseiga when the overly excited quarter-demon had asked him.

Only moments after his release from the Border of the Afterlife, Inuyasha had instinctively put himself in mortal danger to defend his wife and teenage daughter from Kirinmaru's incredibly large and powerful burst of purple demonic energy emitted from the rogue beast king's chest, erecting the pale blue-colored demonic shield around the recently reunited family to withstand its destructive power.

Powers & Abilities

 * Demonic Energy Barrier: it is capable of projecting a pale blue-colored barrier of pure demonic energy, which Inuyasha uses on multiple occasions to save his life and those around him; namely Kagome, Miroku, Sango, Shippō, and his daughter Moroha. It is capable of withstanding both Naraku and Kirinmaru's strong attacks, but will falter given enough damage.
 * Summoning Tessaiga: The sheath is also capable of summoning the Tessaiga from a distance if separated from its rightful owner.

Trivia

 * It is not shown how Inuyasha came into possession of the mystical sheath after obtaining Tessaiga, seeing as it was not where the sword was embedded in the golden pedestal.