One of the Buddhist 5 Vajra-rajas (wisdom kings). They are personified by peacocks because of their habit of preying on snakes (nagas) and symbolize the resistance of terror and disaster. In Vajrayana Buddhism he is thought to be one of the avatars of Gautama Buddha.
In Japan, he is known as Kujaku Myo-O (Peacock Wisdom King) and is also revered as a god of rain prayed to in times of drought, poisoning, and disaster.
Mahamayuri is a foreign demon from India who has taken over Shinjuku in Infernal Tokyo. He has placed a Domain in Shinjuku's underground district and rules from there. He questions who they are and tells Akira that he's never heard of him when he introduces himself. He calls Akira foolish for thinking he can oppose him and that they will not leave there alive. As the battle starts he tells them that power rules the world and that he shall bring all his might to defeating them on the battlefield, asking if they can overcome the power that reigns in the land.
He then summons the Yaksha Horde. After their defeat he joins the battle and congratulates the Samurai upon his own defeat, crumbling afterwards.
"Known as Kujaku Myou-oh in Japan, he is known to remove misfortune, fear, and poison. This is because he is the deification of the peacock, which eats poisonous snakes. He is often portrayed as riding a peacock, holding a lotus or peacock feather, and with a graceful expression, unlike the other Wisdom Kings that are depicted in more wrathful fashion. In Shingon Buddhism, founded by the monk Kukai, it is said he is an incarnation of Buddha, taking that form to enlighten people."