King Silver Song is the king of sirens and The Dazzlings mentor. He wears wears a mystical pendant around his neck that feeds out of conflict from people he controls with his singing.
Long ago King Silver Song ruled over the seas Equestria where he and his siren subjects would cause shipwrecks with their songs then scavenge the the wreckage for anything and everything valuable. Seeking to expand his reign he proceeded on a campain to bring all of Equestria under his rule by spreading disharmony among ponies but was thwarted by Princess Celestia and Princess Luna and banished to the human world where it was beleved that he couldn't do any harm since no magic existed in that world. He taught The Dazzlings how to sing and is the most powerful of all the sirens. During his time in the human world, he took a job as the music teacher at Crystal Prep Academy. He even manged to enroll The Dazzlings as transfer students from Canterlot High School and give them their powers back, although the four of them manged to elude Dean Cadance's suspicions Principal Cinch was skeptical and has been keeping an eye on both King Silver Song and The Dazzlings ever since.
In Equestria, King Silver Songs' appearance is similar to that of a dragon, pony, and sea creature hybrid. In the human world he is shown to possess pony-like ears and translucent wings in his anthro form and can summon an astral projection of his true siren form from his pendant.