Kongōsōha

is a special attack that launches diamond shard spears. The technique was originally Hosenki, he passed the technique on to the Tessaiga, after it's user InuYasha proved his worth by choosing to save his friends over strengthening his sword.

The Kongosoha is able to pierce the strongest barriers, including Naraku's barriers. The attack is not unbeatable, it is unable to pierce the armored shelled of Meioju. The Tessaiga can only use the technique by transforming into it's Diamond form.

Later in the manga the yokai Moryomaru tricked InuYasha into using the Kongosoha on a Meioju (turtule yokai) and than absorbs the yokai along with the diamond shards on it's armored shell, giving him the ability to use the Kongosoha. After Naraku absorbs Moryomaru he also gains the use of Kongosoha, he is able to add his shoki to the Kongosoha to make it more deadly.