Something I've been thinking about recently; the Golden Keys of the Zodiac were and are a pretty big idea when it comes to Celestial Mages. Unlike Silver keys where there is basically a whole species that you can summon from, the Zodiac are individual entities; and as Aquarius proves, there is only 1 key for each Zodiac member on Earthland at any time. Plus there's the fact everyone calls Leo the "leader of the Zodiac", which means they aren't just 12 random powerful spirits: there are acting as a collective.

My question is: what do you think is the canonical reason for the existence of the Zodiac? Zeref obviously used them for the Eclipse gate, Anna was already an accomplished Celestial mage before she got involved, which means that the Zodiac had already existed before them. And Aquarius specifies that the King can only be summoned with a Golden Key specifically as a sacrifice, which says that there is some direct link between the Zodiac and CSK. (Also given evidence with the fact that they are the only ones effected in the Eclipse Spirit Arc, if your the type of person that counts that.)

So what do you think it is that makes these 12 spirits so special, and what type of connection do you think they have with CSK?