Menōmaru performs the inheritance ritual to gain his father's power.
The inheritance ritual (継承の儀式, Keishō no gishiki, "Ritual of inheritance") was a ceremony undergone by the Hyōga clan of moth yōkai. During the ritual, the participant would absorb the power of the previous leader of the clan, or Hyōga, and add all of the power of the clan's previous generations to his own. In doing so, the leader of the Hyōga clan became one of the most powerful and infamous demons of all time. Menōmaru was the last member of the Hyōga clan to perform the ritual, when he absorbed his father's powers to become the new "Hyōga", and when he gets his wings, he summoned his father's armies of demons of the Asian continent the Ming dynasty (originally the Yuan dynasty during its invasion of Japan). Following this, Menōmaru was defeated by the Inu hanyō Inuyasha, and his family's power perished along with him.[1]