What entity might inhabit the weapon of a Tiefling Hexblade with Levistus bloodline?

I’m planning to play a Tiefling Hexblade with Levistus bloodline. The weapon of this Hexblade should be inhabited by an entity that was sent by Levistus. What entity could that be? Demons don’t work together with Devils, so that’s not an option. Another devil? Is it possible for a lower devil to inhabit objects? A ghost like entity seems wrong, too.