You could do a Alu-Fiend, which is basically just a half-fiend, but there are several in some of the Drow FR novels. You could purpose your succubus, as the Alu-Fiend and make her a servant of the Temple instead of the house and give her some priest levels.<br/><br/>I don't think the bebilith would work it seems to be more of a monster than a plotting character, I don't have their stats so I'm not sure how smart they are. A giant spider demon not very subtle either.<br/><br/>