Brain (ブレイン Burein) was the leader of the Oración Seis, a Dark Guild composed of highly powerful Mages whose goal was to find a very destructive Magic known as Nirvana, which was sealed away long ago. Inside him dwelled another, more evil and dangerous personality known as Zero (ゼロ Zero), who acted as guild master of the Oración Seis.

Brain met his death at the hands of Cobra; Zero, however, fueled by the negative energy he accumulated from previously using Nirvana, proved to be a force of darkness too great to completely expel from the world of the living, and this allowed him to be found and saved by the Black Wizard Faris. He then went on to become one of her Oración Sechs. Zero's revival as a Demon also had the side effect of reviving Brain, but Zero took over as the more dominant persona, allowing Brain to emerge when Zero needed to summon his intellect and magical expertise.