A Familiar Bond

Right after overhearing how Sirius Black betrayed his parents, Harry finds a certain little feline in the snowy wilderness of Hogsmeade, and the future changes forever. Bellatrix Lestrange escapes Azkaban after her cousin and somehow finds her master's greatest nemesis at his weakest moment. What if said nemesis decided to make her his familiar? Strong!HarryxMulti. AU.