Orochidayū

was a snake demon.

History
Orochidayū desired to create a duplicate of the Shikon no Tama, but he needed to gather souls of humans to do so. He soon met Gyu-Oh, a human-bull demon mix, who also wanted to create a new Shikon no Tama in order to change himself into a full-fledged human. They soon made a deal: if Gyu-Oh helped Orochidayū create a new Shikon jewel, he would allow him to use it in order to change himself into a human. To further his army, Orochidayū also summoned the toad demon Gamajirō to help process humans' souls.

When Inuyasha and his friends found out about this (Orochidayū used Gyu-Oh disguised as the human "Izumo" to lure them to him) they decided to crush this plot. When Inuyasha was temporarily separated from the group, Orochidayū appeared out of the shadows and attacked him. After pursuing him, both of them ran into Gyu-Oh (who had revealed his true form) and Kagome Higurashi. The snake demon then changed into his true form. Inuyasha killed him soon afterwards.

Trivia

 * He greatly resembles Daija, the false water god, for some reason. It's possible that it is just because that he and Daija are from the same demon species or that Sunrise media just recycled Daija's character design for Orochidayū. They both share the same English voice actor as well.