[QUOTE=Shienvien]Original devils, devils whose nature embodies being a fully evil devil the most - archdevils? (As by nigh the definition of arch- as a prefix.)[/QUOTE]
Eh, to be honest I'm not even exactly sure what you suggest "archdevil" would denote. For starters, Prophecy devils are not all deities - in fact the vast majority of them are just the kind usually classified as greater demons - and not all evil deities are devils (with some instances of this being quite obvious, such as with Kreshtaat, who is, by Prophecy-definition, a demon). If "archdevil" were to denote devil deities, then, I would probably have to call the demon-deities "archdemon", which would also be the common name for all of them, since "demon" is the wider of the two terms. And somehow, especially archdemon, but to an extent also archdevil, at least makes me associate them more with archangels than with gods, which would still make them sound as "less".
I think that if I was making the Prophecy-universe today - because I'm quite beyond being willing to change it - my personal way of handling it would be to simply forgo distinction between the two opposites and refer to all of them - good and evil - as "gods".