Asura (阿修羅, Ashura) was one of the twelve demons that made contact with Kagemitsu Daigo. That had appeared as a statue ever since in Episode 12. It wasn't long until make it actual physical appearance in Episode 22 possessing Mutsu, Hyogo and Tahomaru after they made a pace to him to restore them with eyes and arms after being sliced by Hyakkimaru from the previous battle.
Appearance
Asura took the form of the three head and six arms with three eyes each on its face.