Leonis Black, Son of Darkness by Light

Despite being a lion, Sirius still became a Death Eater. Despite being light, James still loved him. That love manifested in a son. 12 years later, after escaping Azkaban, Sirius must protect his son at all costs against both darkness and light. 12 years later, Leo Potter discovers he's actually Leonis Black! AU (Begins 3rd yr) - Coauthor Septima Holen!