“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.
The Forbidden Magic impregnates a host body with a parasite that is known as a “Kinjuu” (禁獣) or “Forbidden Beast”. The results of completed incubation of the creature has been noted to take control of the host’s body through symbiosis, resulting in suppression of the host’s consciousness or destruction of the host’s body outright (through overexhertion or a form of pressurized “birthing” which makes the human body explode and/or mutate).