That was just a random apt-feeling thought I got as I was reading your reply to me, which I then quickly jotted down after briefly checking the prefix against a dictionary, just in case it also had other meanings in addition to those I was personally aware of. (It was also about five minutes before I left the house, and I more or less haven't had the chance to use a computer since.) In essence it was an idea on how one could potentially distinguish a "regular" devil (in the sense of [i]any[/i] evil deity-level entity) from an Ismyel-created devil. - An Ismyel-created [i]non[/i]-deity-level entity would be archdemon, by that same logic: any non-deity infernal entity would be a demon, any deity-level infernal entity would be a devil, and if either was one of the Ismyel-created ones, then it'd be archdemon or archdevil respectively. 
	I was unaware that there were non-deity-level Prophecy-devils before your last specification, though (that's even odder thought, devils which aren't even deities; while "demon lords" have predominantly been significantly below deity-level, there is certainly also a very strong assignment of "devil" to a minimally deity-level entity or primary force).
	Ehh... Semantics, we meet again.