The world nearly ended, only the sacrifice of one of their own prevented everything from ending that day.
Her sacrifice brought them not salvation, but time. Time to prepare, to do what must be done to save the broken world she'd left behind. To save the broken friends and family she'd left behind.
Three young ponies, each linked to an element bearer in their own way, each with the weight of the world on their shoulders. Three young ponies that are the only thing standing between the remains of their world and the end of it.