In the dragon graveyard, Arcadios explains to Fairy Tail what he needs from them to make Project Eclipse work. He takes them to the king's palace, Mercurius, and shows them Eclipse, the actual portal designed to take a party back in time to kill Zeref! But not everyone in the kingdom is on board with changing history...
The power of a Celestial Spirit Wizard was 
necessary to the secrecy of the operation.
قوة ساحر أرواحٍ سماوي كانت لازمة لأجل سرّية العملية