Episode 18

Naraku and Sesshomaru Join Forces is the eighteenth episode of the InuYasha anime. It first aired in Japan on March 5, 2001.

Synopsis

 * 1) Naraku gives Sesshōmaru a human arm, with a shard of the Shikon no Tama embedded within it, so that he can wield the Tessaiga; he also gives him the hive of the Saimyōshō, to combat Miroku's Kazaana.
 * 2) Sesshōmaru steals the Tessaiga, and uses it against Inuyasha; Sesshōmaru utilizes Tessaiga's true power, the ability to destroy 100 yōkai with a single stroke.

Summary
Sesshōmaru receives a human arm with a Shikon Jewel shard embedded in it from Naraku as a means to wield the Tessaiga and destroy Inuyasha. Miroku discovers that his wind tunnel can be inhibited by the Saimyōshō, the poisonous wasps from hell.