Calling of Bones

The caster (must be a bone servant) concentrates, and reaches out to touch the skull. Upon contact with the skull the caster starts shaking violently and bleeding, the skin turning a dark gray, growing larger and larger as the skull combines with the casters own head. once the three minutes are up the caster loses all sense of humanity and reason, attacking anything that moves going on a rampage. The more this spell is cast the more the casters body resembles the bone god permanently, this is only reversible through ritual.
(Spell is casted faster upon each size upgrade, and body change is sped up per level.)