this is my first fImfic so lay on the tips please!

Darkness. What do you think of when you here that word? Perhaps Scary, horrifying, and maybe even lonely. The truth is though everything has a little darkness to it. Even the brightest of things have something terrifying hidden inside.

Celestia has made a dire mistake. She has sent something accidentally and unwillingly out into Equestria. This Monster is called Black Sun, the part of Celestia that she had desperately been trying to suppress into her subconscious for 100 of years. This creature has been sneaking across the wide lands building its power up to it's full height to try and destroy Luna, the Princess of the Moon. If Moon can last forever why can't the sun? Though this thing was part of Celestia she refuses to let the sun rule alone, and blocks the way to victory for Black Sun. So Black Sun turns It's eyes on targets that can weaken Celestia completely… the keepers of the Elements of Harmony.
Wanting to protect her little ponies but not let any one discover her mistake and panic, she sends out a Captain that she trusts to protect them. She sends Captain ShadowDust to the Town of Ponyville to keep an eye on them all but warns her not to grow any personal emotions to them just in case something went wrong. Can Celestia face her Mistake? Can ShadowDust protect the Ponies she was assigned to? Or will something go very, very wrong.