Twilgiht Sparkle and her friends had defeated Nightmare Moon, purging Nightmare from Luna's body. They had defeated King Sombra, destroying his body and saving the world. For this, Twilight Sparkle was made a princess.
That was ten years ago.
Now, Nightmare has found the remains of Sombra. together, they form Nightmare Sombra, with only one goal in thier head: revenge. Revenge on the Elements of Harmony for ruining thier plan. Revenge on Celestia and Luna for shunning them. Revenge on Equestria for the hatred towards them.
Soon, the Elements are no more. Celestia and Luna agree to help make a new Alicorn: Daylight Dusk, with the powers of the Dawn and the Evening inside him. Thrown back in time, Daylight Dusk must warn his parents's past selves of the danger, and stop Nightmare before she finds Sombra's remains.
This story is rated "Teen" for the following reasons: violence, language (at times), and character death. You have been warned.