Triad of Ignis

Harriet Potter was a planner, she didn't get involved until she knew every aspect of the challenge and every escape route. Unfortunately, she didn't exactly have time for either when the Pendragon Royalty and two mischievous twins get involved. Fred/Fem!Harry/George, BAMF!Harriet, Grey-if-not-dark!Harriet, Suspicious!Dumbledore, Bad!Voldie, Good!Slytherins, Basically-Good-Hogwarts