I wrote up my Devil entries today.
The list contains:
Mephistos: Vice - Pride. Schtick? Contracts and ego stroking.
Malebranche*: Vice - Envy. Schtick? Secretly buffing one member of a party.
Erinyes: Vice - Wrath. Schtick? Pissing people off.
Succubus/Incubus: Vice - Lust. Schtick? Seduction.
Belphegan: Vice - Sloth. Schtick? Get rich quick schemes.
Mammonite: Vice - Greed. Schtick? Telling you exactly where the loot is (nothing more).
Beelzebal: Vice - Gluttony. Schtick? Party till you puke.
Pit Fiend: overlord of the devils. Schtick? Kicking your ass.
Hat tip to Collin de Plancy. Demons, I decided, will just be interspersed throughout the other monsters, rather than as their own "type." Why? Because devils are fallen angels, so have a bit of "Law" to their make-up, if no longer their natures. Demons are just pure Chaos/Entropy.
Now, do I want to do the Choirs of Angels? Something to think about.
*I couldn't do this without at least one nod to Dante.