When a key to the past turns up at her door, Fleetfire Bittermane just has to investigate. What she doesn't know is that Equestria is under threat from an army of two-legged magical beings. What she is about to find out is that her destiny is entwined with the Harmonosphere, the keepers of peace. She must leave her own personal issues to rest and be ready for what is to come. But will she?