I would be interested in playing an antagonistic character. Perhaps a rival demon lord/lady looking to take primary demonlords lands by any means necessary ( political machinations, cleaver manipulation, all out war if needed ) 

Alternatively, but far less easy to regularly fit into the story I have this idea of a Miko who died tragically and violently in a manner involving demons, who has now turned into this very powerful vengeful spirit wanting to rid the world of all demons and any who cling to a demons power. 

Perhaps both could play a role? The rival lord being a more constant character with the Miko being sort of this dark horse figure on the edges of of the conflict until a more climactic point?