What about potential option C? Kill Lucius. Make Eridanus watch..

[ yes, he manages to make this suggestion just fine while still petting her hair, sipping the drink he has in his other hand. ]

Maybe he will wake up when he's faced with the reminder that Lucius is just another average monster trying to survive on this peninsula. Besides, you tossed him out but he's essentially a child you've sent to his room as a punishment, where he can entertain himself perfectly well.

Consider taking his toy away instead.