- Shin Megami Tensei III: Nocturne: Antagonists
The Mantra Army is a collection of various lowlife ruffians and thugs under the banner of controlling post-Conception Tokyo with a philosophy of "might makes right". The group initially proved unstable until its leader, Gozu-Tennoh, reached a reliable right-hand man, Thor, who gave it a semblance of order and allowed its ideals to be developed a bit further. The group was based upon the Mantra Headquarters building in Ikebukuro, and maintained a large facility for the absorption of Magatsuhi in Kabukicho.
Given their ideals, they were the sworn enemies of the Assembly of Nihilo.
The Demi-Fiend entered the Mantra HQ with the initial intention of following information trails about his friend, Isamu Nitta, only to see him brutally assaulted by Thor and being imprisoned himself, and forced to attend a warped "trial" in which his defense was to be subject to a gladiator-style match, first against Orthrus, then Yaksini, and finally against Thor himself. Besting all three allowed him to "prove" his "innocence" and was thus released on Thor's authority.
Following this, he met Gozu-Tennoh, who decided to march against the Assembly in their Ginza base. The raid was apparently successful for a brief while, before the Assembly activated their secret weapon: the Nightmare System. Ikebukuro was its main target, and before long the entire Mantra Army was on its knees. The Demi-Fiend briefly managed to meet with Gozu-Tennoh a second time before his apparent death; the demon vowed to remain, unwilling to allow the Assembly's goals to come true. His assistant, Thor, repeated the oath as he left Mantra's headquarters.
Much later, Chiaki Tachibana seized control of Mantra's assets by fusing with the spirit of Gozu-Tennoh and resurrected it as a major power in her bid for godhood in the new world that was to come, filling it with Divine-race demons interested in her idea of the new world. An Oni complained ex-Mantra forces were discriminated against by the newcomers.
To fuel the summoning of her god, Baal Avatar, Chiaki led an assault force upon Asakusa and Mifunashiro, destroying the Manikin colony there and summoning the archangels Gabriel, Raphael and Uriel to battle the Demi-Fiend in case he did not agree with Yosuga's ideals; otherwise, she forced a confrontation between him and Futomimi.