“Hi-Deigokutsuipo” also known "6 Forbidden Magics" The Forbidden Magic was named as such because of the danger posed to humans upon enchantment. Zato=ONE sacrificed his eyesight as a “password” to obtain control over his shadow, meanwhile it is suspected (though unconfirmed) that Millia Rage (unwillingly) sacrificed her ability to have children in exchange for control over her hair as a weapon. The main reason a sacrifice is necessary is with every Magic incantation a certain about of Horiki (法力) or “Mana” is required to execute the Magic spell or “Houjutsu” (法術). The sacrifice is something similar to a symbolic exchange that produces the Mana necessary for the “Binding” to take place.