(i have an idea that’s not so much an episode as it is either a season arc or a mini-series of shorts. basically, the mane eight easily handle some new wannabe villain and end up letting them go because no real harm was done. meanwhile, Chrysalis has found and made herself read a copy of the friendship journal and believes she’s found how those ponies keep besting her. they evolve and grow stronger through learning from their experiences. she recruits the wannabe villain from before and tells her to go out into the world, keep trying to do bad and send her reports about what she’s learned. basically, Chrysalis wants to be an evil Celestia and cultivate an evil Twilight to grow strong and aid her next time she attacks Equestria.)
Nightmarriage part 1 The Smooze, while shlorping around the frozen north, happens upon Sombra’s horn. Unfortunately, it doesn’t notice until it’s already let it make contact and push itself and Sombra’s will into its body. The Smooze, being a fairly simple-minded creature, is easily taken over. With Smooze’s abilities and Sombra’s malice, Equestria seems more doomed than ever. Discord can tell it isn’t acting like itself and looks into it, finding out what’s happened and suggesting that if Sombra didn’t have magic to influence Smooze with, it would go back to its mostly-innocent self. None of the princesses knows how to take magic…but they know someone who does. They travel to Tartarus to ask if Tirek will show them how to steal magic and he says he will, for a price. He will teach it to one of them and 24 hours after they learn it, whether it works or not, she must return and stay in Tartarus forever. As his bride.
Nightmarriage part 2 Luna volunteers to be the one to learn the spell, since Celestia has proven she can rule alone, Cadance has a family and Twilight has her whole life ahead of her. Tirek teaches her to steal magic, noticing how out of it she seems during the lessons, like she’s sleepwalking, but he chalks it up to not exactly looking forward to her future. Finally, the time comes and Luna confronts Sombra-Smooze. After a nice, exciting battle, Luna finds an opening and begins to steal Sombra’s magic. She sends the magic she took into space, tells Smooze it wasn’t responsible for what happened and returns to Canterlot Castle to prepare for her wedding. She suspects that she’ll only be there for Tirek to take magic from until he grows strong again, but she made a deal and must honor it. When Equestria finds out about this, they treat her impending wedding like a funeral. There’s a nice little scene of the other princesses, including Flurry Heart, saying their good-byes to her.
Luna enters Tartarus and Tirek comments on her lack of wedding dress. She tells him that she isn’t marrying him since she didn’t learn the spell. What he assumed was pessimism really was her sleepwalking through the lessons. It wasn’t Luna he taught, but the Luna that appears in dreams, listening to him from within Luna’s own dream. That figment taught her to steal magic, and it will be his bride. Tirek tells her that dreams aren’t possible in Tartarus, and she basically replies “Well, that’s a shame, but I tried, see ya never”. She leaves as Tirek vows she will be his and the mourning turns into a triple-celebration that even Pinkie can barely manage. Celestia asks if that was her plan all along, and Luna says “I would give everything for Equestria’s safety, including myself. …but a plan that works out for everyone is almost always better than self-sacrifice”. Or something like that.
