Recompense (George Weasley)

Ten years have passed since the battle of Hogwarts. Philomena Gryphon, a muggle, discovered the existence of magic as her sister had been investigating the world of Witchcraft and Wizardry long before the battle.

Philly knows who the Death Eaters are, and though Lord Voldemort has long since fallen, there are others that are alive. She knows their names. She knows where they live. She's spent 10 years preparing to bring things full circle, developing the technology to deflect magic. She will stop at nothing to wage war against the Dark Wizards, to avenge the innocent. And she's bringing backup.