By introducing positive feedback into the seithr contained within the Grimoire, the "power" contained therein can be safely held within one's body.
In XBlaze – Code: Embryo it was said that only Tōya Kagari is capable of this and, when in this state, will not absorb the life force of those around him. In XBlaze – Lost: Memories this ability was also used by "Me" (Original Grimoire), Freaks (New Testament Grimoire), and Es (Phantom Grimoire).
Tōya was taught this command by the Phantom Boy (幻影の少年 Gen'ei no Shōnen), the "other" Tōya Kagari that was awakened when the power of the Grimoire was unleashed. Until then, he was trapped in an endless dream. As he controls the level of power available to Tōya when he uses the Grimoire, he calls himself the Arbitrator (調停者 Chōteisha). He exists in the deepest depths of Tōya's subconscious and can only be encountered while sleeping or unconscious, though the memories of any encounter will disappear upon waking. It is unknown where his existence came from, though he said it could have been born by the seithr from Ripper or it could have been born as a self-defense mechanism.
Code: Soul Eater! XBLAZE, IGNITE!