Not as a human, not possessing a purely good heart, called "Saul," the demon's egg casing.
Nor is it that which Annan jokingly calls "Vatore" — or, "everything in Salvatore except 'Saul'": the demon yet to be born.
But instead, it is a new form never seen by Annan.
"...Have the senior brother and senior sister integrated into one?"
Annan muttered.
The Curse Binding possessed by Salvatore, named "The Unsleeping Reflection," is one of the ten "Reflection" Curse Bindings. Only pure-heart individuals can own a "Reflection" — this Reflection can absorb all their negative traits, ultimately cultivating them into the most holy and virtuous of beings.
Conversely, if the Saint acting as the vessel is corrupted by curses to the utmost, the roles reverse— a fully developed demon is born from his body — it is the most wicked and vile of demons, possessing traits completely opposite to those of the great man, yet inheriting all his power, the "Successor."