Gyanon (戯阿音(ギャノン)?) is one of strongest Horrors in existence, labeled as Messiah's Fang (メシアの牙 Meshia no Kiba?) and the Ancient Red Demon Beast (太古の赤き魔獣 Taiko no Akaki Majū?). Having seemingly died, the Makai Senate sent a group of three Makai Knights and one Makai Guide to retrieve the monster's corpse from Amber Rock Valley. However, Barago also sought the Horror and Gyanon was no where to be found by either party. It is revealed in Makai Senki, that Sigma Fudō had stolen Gyanon as he intends to utilize the Horror in powering up his Magōryū Idea while reviving the fiend with large numbers of human sacrifices. To achieve this goal, Sigma obtains the pelt of a Spirit Beast to ensure the revived Gyanon is under his complete control while infusing Kouga's body and soul into the Horror to complete his resurrection. Though Kouga is freed, Gyanon awakens after Idea's creation in response to Sigma's darkness, devouring him and assimilating the ultimate Gōryū while assuming his androgynous human-like form. While telling Garo that his resurrection was unplanned, Gyanon intends to take advantage to bring all Horrors into the human world. However, Idea is destroyed with the Makai Knights and Madou Priests joining forces with Gyanon reduced to a head as Garo destroys the bodiless Horror.

Gyanon is portrayed by Peter (ピーター Pītā?).

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