Long ago, Starswirl the Bearded banished three sirens to an unknown world where they can no longer cause any more harm to pony kind. However, little does anypony know that the history of this isn't exactly true. There was in fact a fourth creature that was banished with the sirens, one who was unrightfully banished. His name is Draco.
He has been friends to the sirens ever since. Even now in the sirens darkest time, Draco will do anything in his power to help keep his only friends alive. Even if push comes to shove with the elements of harmony.

Canon to the Era of Harmony.