My Little Pony: The Golden Prince

Lance, the prince of Equestria, has the incredible power of light and darkness. Ever since he was a young pony, he was kept away from the kingdom for his sister, Nightmare Moon, might use his power to cast eternal darkness to Equestria. Now, Lance returns to Equestria and was sent to Ponyville to take care of a few things for a celebration, the longest day of the thousandth year, Nightmare returns and tells Lance that either he helps her bring darkness or let Nightmare destroy Equestria and all living ponies in it. With the help of Twilight Sparkle and the others, they venture on a quest to use the element of harmony against Nightmare Moon.