This story is a sequel to The Return of the Shadows

Princess Celestia sends King Sombra to Ponyville to learn about friendship with Twilight and her friends.
But days passed, and between Sombra and Twilight something else grows.

Years have passed since King Sombra was defeated, but the ruler of the shadows was risen from the ice mountains.
Now, he has a new plan, something that will surprise everypony.