User blog comment:Omega natsu2/Episode 192: Live on for Her, Review./@comment-24053170-20140726035822/@comment-4829046-20140727094654

@anon That's not what Sage meant. If Zeref supposedly knows how to utilize CS power then makes sense that his Demons or at least the oldest of his demons have met the CSK. That and also the theory that Zeref may have created the CS keys also falls in.