He nodded slowly, thoughtfully. He trusted Freyja's intuition as much as his own, so he believed her when she said she took these feelings seriously. "Possession could be a number of beings, from a number of cultures," he said. "Spirits, demons, other gods... It may required some research to pin down exactly what it is to find it's weakness and rid your brother of it." He went along the shelf, looking for books that may be of some help. "You say he won't let you into his home? Perhaps he has a shrine of some kind that is the source of his strength, that he doesn't want you to see."