So, this seems to be a source of some small amount of contention. Some people say there was word that the Archfiend set would be available via Trophy Crystals, while others have said that may have been a mis-translation. Or it's also possible that perhaps that was the plan, but it was changed for some reason.

I can't speak for anyone else of course, but I would certainly love to know whether or not that might eventually be attainable again, or what the plan is on that.