Find the Sacred Library
This one's for KOHO
According to Tenebris’ brother, there is a single place in the castle Tenebris is magically barred from. After his fall to the darkness, his patron goddess Ilthea cursed him to never have access to the Deep Knowledge he sold his soul for. According to Tenebaum, he has a key, but is blind and cannot get there himself, but thinks he could remember where the entrance is if he can go feel around with his magical fingies.