Brio Vespers is the last siren in all of Equestria, and public enemy number one. On the run from the royal guard, all he wants is to have a home like when he was young boy. But as he tries just to get by, he finds himself on a journey to find the abandoned City of the Sirens. It may hold the secrets to the past and his future, tell him whether he can be good, or if what his decides who he is. But his life isn't the only one on the line. From the shadows, an unknown threat endangers all Equestria. It may have more to do with Brio's journey that he realizes.

Takes place in the Nurtureverse, an AU where Apple Jack raises a baby siren. Below are a list of stories that take place in the same universe. They are not necessary to read to understand this one, but reading "The Nature of Nurture" is highly recommended, as it's the universe's main story.
The Nature of Nurture
In Which Rarity Ships