Messiah the Ultimate Horror (究極のホラー ・ メシア, Kyūkyoku no Horā Meshia) is the progenitor of all Horrors in both the Original Series and the Ryūga-verse series. An immortal being, she can only be defeated, but not destroyed. In the original series, Garo defeated Messiah; in the Ryūga-verse, she awakens and traverses through the Makai Realm.
Messiah is the originator of all Horrors from the True Makai Realm (真魔界, Shin Makai) and existed since the beginning of the conflict between Makai Order and Horrors. Messiah is the most unusual Horror, even among legendary ones because she's the only Horror that appears almost perfectly human in form, resembling a giant white-skinned half-naked woman with long-clawed fingers and unique jewelry and tattoos around her head and shoulders. Her back contains a Taoist halo.
Due to limited exposure, more of Messiah's character and origin weren't completely defined. What is known about her is that she's highly intelligent and a patient planner. An immortal being, Messiah can never die so long as there's darkness in human hearts. However, her spirit requires immense levels of darkness to resurrect herself (approximately 1,000 Horrors) and a girl born on the sixth day of the sixth month which marked upon her 6th birthday as a vessel to give herself a physical form. She also indirectly responsible for creation of dark arts within a Madō Book from which her shadow manifest to guide the Dark Knight Barago in acquiring power of darkness.
The events of Fang of God revealed that in addition of masterminded the events of GARO, she also sought to invade Ryūga Dōgai's home universe as much as Saejima family's, enlisting many of her brethren to do so with only Rinza whom close to succeed with use of Fang of God. While Makai Order in both universes have limited records about her, it's obvious that unlike in Saejima family's home universe, Messiah's reputation as legendary Horror in Ryūga's home universe is greatly shadowed by the well-known Zedom.
Though Messiah longs to enter the human realm, despite all her powers she cannot cross through without a large source of energy. After sensing Barago's desperation for power, Messiah reveals herself in a Madō Book that contains forbidden techniques. Though only a shade, Messiah offers to give Barago knowledge and power of the forbidden Makai methods in return to bring about the legend of Kiba. Barago wholeheartedly agrees to give up his soul for power and Messiah proceeds to start him on his path of destroying lives to set up the conditions to summon her in her full glory through Kaoru, who is a suitable vessel due to the conditions of her age and birth.
But once he fulfills his part in her summoning, removing any trace of humanity in him, Messiah absorbs Barago using Kaoru's body as a medium upon being awakened to use his power to complete the process. Her plans to reach the human world are foiled by Kouga, who enters her realm and defeats her with spiritual help from Kaoru. She is ultimately defeated when, overconfident with her powers, she runs his sword into her head and releasing Kiba in the process as she is forced back into her dormant state.
Though overshadowed by other legendary Horrors such as Zedom, Messiah is still has significant influence over her brethren. Her acolyte Rinza sought to revive Jinga by tricking the Makai Priestess Banbi into harnessing the power of the Garo, Gai, and Zen armors so she could use him as necessary power source for the Fang of God. Rinza attempted to restrain Jinga and Garo during their duel, only to find out that Jinga had knowledge of her intent beforehand, gaining a second wind that allowed him to kill her before she could put it into motion. However, the attempt was more than enough to draw Messiah's attention to the Human Realm.
Upon his second defeat at the hands of Garo, Jinga awoke within the Makai Realm just in time to see Messiah making her way to an unknown destination. His wife Amily appears, asking him whether he can defeat Messiah; his response being to morph into his Demon Beast Armor and charge her head-on. The outcome of the encounter is currently unknown.
Being a legendary Horror, Messiah is an immensely powerful adversary that Makai Order and Golden Knight Garo ever faced. Her powers include ultra-human strength, high combat capabilities (while possessing Kaoru and through physical avatar), magical shielding, energy attacks, able to summon Horrors by merely touching the ground she walks upon, and flight. The full range of her powers were never revealed as Golden Knight Garo Kouga defeated her before she reaches her full strength, suggesting she has a larger range of combat capabilities.
- Though the word "messiah" is commonly associated with Jesus, the Messiah from the Bible, it also means "a leader or savior of a particular group or cause". This likely refers to her status as the greatest of Horrors.
- Messiah is one of the few Horrors whose natural form is human-like in appearance. The other two human-like Horrors are Karma and Gyanon.