The Lost Sister, a HP fanfic

Everyone knows Harry Potter's story. The boy who lived, there's not a single wizard or witch that hasn't heard of him. Less famous is the story of his twin sister, known to be dead, killed with Lily and James Potter the night the Dark Lord went to kill the boy.
Lucy Potter is that sister. The one that was forgotten, hidden just under everyone's nose. Kidnapped by the death eaters that night, she grew up to be just as cruel as the Dark Lord himself, but deep down she had so much more. And when she finally manages to escape her dark faith, she finally meets the one she had been looking for her whole life.