User blog comment:FairyRaven/Fairy Tail Chapter 375: The Supernatural, Review and Commentary/@comment-7418318-20140317103924/@comment-5303512-20140317191449

Well Magic does rely on Ethernanos and I suspect Curse has another source like that.

But I think they are like the Celestial Spirits, they cannot survive in the human world for too long or it will sap away at their life force, just like Demons cannot be away from the Cube for too long.

I still think that Laxus is in a class of his own of strength, and Natsu's scarf is the seal for E.N.D and is the reason for all of Natsu's unexplained wins and ass-pulls.