Little Bewitcher Maid

Dumbledore allows bewitchers and wizardesses, wizards and witches with merpeople abilities, to come to Hogwarts. And Sirius goes. The tale of the Mauraders begins with Sirius transferring to Hogwarts. He spends time forging his path in a rapidly changing world. The Wizarding world forces Sirius come to his world from the other side as war begins.