When King Sombra remained dormant and sealed in the Frozen North of Equestria, he was still able to terrorize and conquer within his own mind. Pushing through the nightmares for centuries on end, he had been slowly draining the power of another dark deity while she was imprisoned in the moon. Sapping away almost all of her strength, Sombra was able to reform and return to claim his Empire once more. Throughout his journey towards his rightful Kingdom, he had relished in the destruction he caused along the way, and slaughtered anyone that got in his way. Those included in the massacre were a family of Dragons...

Cover Art belongs to Dreatos from Deviantart.

https://www.deviantart.com/dreatos/art/Take-off-your-helmet-Nightmare-Moon-467545858