When the spirits take the form of the Beast in Volume 16, they taunt Guts by saying if he continues on his path then he'll turn into a monster in human flesh, or that he might become a real monster like his friend.
This naturally points towards the Behelit, but I have a little speculation of my own here. During the usual occultation, the Apostle or Godhand to be forsakes their humanity, and is given a new form, which seems to be a reflection of their soul. They get great power right then, their spirit manifesting in the physical realm.
Now let's look at Guts. He already walks between the astral and material plain, and his force of spirit (an astral concept) affects the material realm. If he forsook his humanity altogether, would he turn into an actual monster without a ceremony?
This naturally points towards the Behelit, but I have a little speculation of my own here. During the usual occultation, the Apostle or Godhand to be forsakes their humanity, and is given a new form, which seems to be a reflection of their soul. They get great power right then, their spirit manifesting in the physical realm.
Now let's look at Guts. He already walks between the astral and material plain, and his force of spirit (an astral concept) affects the material realm. If he forsook his humanity altogether, would he turn into an actual monster without a ceremony?