Octavia is one of the major antagonists in GARO: The Carved Seal of Flames.
Originally, Octavia was a normal resident of Valiante until the day she renounced her faith in God the day her parents and sisters were torn to pieces by wolves before her eyes. Octavia then witnesses firsthand Mendoza's power, the "power of the devil"., and saw it substantial enough to become a fanatic to the excommunicated Makai Priest and his cause. Mendoza accepts his acolyte on the condition that she never touches him. As Mendoza's right hand, Octavia is one of the few people to know the truth of the witch hunt that killed various Makai Knights and Priests.
Even after Mendoza's assumed death, Octavia continues to serve at the palace as no one is aware of her involvement with her master's plans. When placed in a situation were her association with Mendoza would be exposed, cursing being left with no alternative, Octavia is forced to sacrifice her right leg to the summoned Horror Resume to avoid being discovered by Alfonso San Valiante, Ema Guzmán , and León Luís. Later, fueled by her hatred of Makai Knights, Octavia uses the power of Mendoza's staff to transform herself into a monster as the ultimate sign of her devotion to Mendoza. Ultimately, Octavia is killed by Ema after inflicting a wound on her.
Demon Beast Armored Octavia (魔獣装甲オクタビア Majū Sōkō Okutabia) is a form Octavia assumed after using the power of Mendoza's staff. The Demon Beast Armor covering her body is powered by her hate, slowly eating away at her life force.