Secretariat Comet

The Secretariat Comet was a comet that was visible in the night skies of Equestria.

History
Whenever the comet would pass through the Horsehead Nebula by Earth, the magical powers of all magic beings would increase by tremedous amounts. Queen Chrysalis sought to use the power to her advantage and kidnap he Cutie Mark Crusaders, forcing the Mane Six to travel to her realm as the comet passed by. As this was going down, Princess Celestia fortified her kingdom, mostly Canterlot against other threats. Spike traveled to Canterlot to get her help, but ended up in fighting in the battles to save Equestria instead.

Twilight and Chrysalis fought as the comet increased their powers, though Twilight won extremely handily. Despite this, she used up to much power and collapsed. After she woke up, she was greeted by a happy, but wounded, Princess Celestia and the group rested beside a fire, taking in everything that just happened.