I always make sure my stories are happy and carefree in the beginning but then change the tone completely into dark and gloomy. Because it's My Little Pony. Make it dark.
Set in the BoD Universe. When Twinkle abruptly renters Zany, Applespike, and Jewel’s lives, they learn of a power Twinkle has been keeping hidden for 15 years. Now, they must help her overcome a problem that may keep one of them stuck in a nightmare.