The soul is one of the party's enemies, a CE psychopathic changeling enchanter and alienist to whom my LE psychopathic changeling sorcerer took a shine (based on obvious similarities).

Should he return, he'd probably just be imprisoned for life, so he's none too eager to come back at all.

Abyss-diving would be difficult for a variety of reasons, mostly due to my character's close connection to devils. Even if we knew specifically where to find him, it would turn into a nasty battle with endless hoards of demons pretty quickly.