|Think I've seen you somewhere before|
Sure, you could head to Appendix D and get something like a purple bison with moth antennae.
Or .... head over to the Demonicpedia, which catalogues all demons from historical grimoires, claviculi, and folklore. Then your evil cultists can be invoking...
Lord of Swords and Eyeliner
... but peaceably
OK, they can't all be scary