((Like I said he's not the kind of colt who gets involved, again even if he wanted to))
Brightest Dark began to get sleepy, closing the book he turned around to Princess Luna in the shadow of the tower. Shocked he stumble back over the book and fell on his hindquarters, he was afraid because Luna looked furious. ((A lot of dreams are going to be nightmares at first.)) Princess Luna looked down at the book and back up, "Just as I thought some silly pegasus was reading my journal! Who do you think you are reading the personal journal of the Ruler of the Eternal Night!?."
"I…I am sor-sorry your highness didn't realize that..." Brightest Dark stammered trying to play dumb.
"Didn't realize?! Now you lie to me? To Nightmare Moon!?" She stepped out of the shadow showing she indeed was Nightmare Moon.
Brightest Dark stared confused, "Twilight and her friend defeated you with the Elements of Harmony! You returned back to being Luna."
"yes well it seemed they where not careful enough now where they?." Nightmare Moon smiled slyly, "you seem like a smart Pegasus. I will forgive you reading my journal and in exchange you will help me. We can force the Sun to follow the Moon!"
"help me?"
"Yes of course not physically but I will guide you to power in your dreams"
Brightest Dark grew suspicious, "so the they really did defeat you? And this is just a dream? How can you help me if this is just made up?"
Luna looked down at Brightest, "this the real me, that," she pointed to her evil counterpart, "is a manifestation of some darkness inside your heart. You have to let go of whatever is before it consumes your life. This you must do on your own, my power does not extend to your heart so I can't entirely see what torments you."
Luna hovered the book over to them, "as for this, I shall expect you to write me a story in here about a young colt training to be a Wonderbolt as punishment for reading on my private book. Include puzzles to would you? I'm am quite fond of them."
As soon as her sentence ended he woke up, he could still feel the softness of her feathers. Looking around he got up and stretched before looking out at the dwindling sun, his dreams alway last such a short time. Remembering Nightmare Moon he shuddered, but what if she could help him get better than his sister? What if the moon was followed by the sun? I must be going crazy, he thought to himself aware that the thought would always be there.
((ok that was not just some new power inside him, or Nightmare Moon coming back, he made it all up. He is serious moon-mad, a (forgive me for this) Lunatic so to speak. The nightmare moon was a manifestation of … well can't divulge everything yet! But rest assured I am not trying to force a plot twist, just adding depth to the character. Spike is to Brightest Dark, as Rarity is to Luna))