User blog comment:Miskos3/Fairy Tail Anime Returns in April/@comment-5840892-20140317032513/@comment-7418318-20140317083406

I wasn't too fond of having a seal for every teensy weendy bit of magic. For example Happy's Aera getting a seal in the fight against Erigor was just plain weird.

I prefer the seals to only be there for only few selected spells, like Abyss Break, Fairy Law or Milky Way, so that the seal can signal "something special is coming". A bit like the way Magi handles the metal vessel's powers and their extreme magic.