Tenseiga

The sword has a special property in that it cannot harm any living beings, which is ironic for a sword and for it's wielder Sesshoumaru. 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.

The Tenseiga was created by the swordsmith Totosai from a fang of the daiyokai the Inu no Taishou the father of InuYasha and Sesshomaru. The Tenseiga has the power to cut beings of the next world such as pall-bearers who that take away the souls of the dead, this allows the Tenseiga to revive the dead. Tenseiga can revive 100 people with one swing, the opposite of the Tessaiga's ablitiy to slay 100 yokai with one swing. After the dog lord's death Sesshomaru was left the Tenseiga.

Originally Sesshomaru did not wish to have Tenseiga, because it could not be used as a weapon and he began to search for his father's other sword the Tessaiga. However the Tessaiga was left to his younger brother InuYasha and had a barrier which prevented him from using it, forcing him to look for another weapon. Sesshomaru hated humans and this prevented him from being able to use Tenseiga. It wasn't until he showed compassion and sorrow for the human girl Rin, that he was able to use Tenseiga. Upon using it's power did Sesshomaru start to value the Tenseiga.