Transformers/Star Wars/Harry Potter: Conquest is a crossover fanfiction. It takes place in an alternate universe (or rather, two) to Transformers, Star Wars, and Harry Potter.
As the story begins, Harry Potter is now trapped by the three Death Eaters Lucius Malfoy, Bellatrix LeStrange, and Fenrir Greyback. Helpless without his wand, Harry closes his eyes and waits to die. Seconds before he gets three Killing Curses at the same time, a mysterious figure in red armor leaps in and deflects the Curses, killing Bellatrix LeStrange and Fenrir Greyback. However, Lucius Malfoy manages to narrowly evade death. Before Harry can thank him or ask his name, the mystery man is gone, but he does hear a strange sound like some otherworldly machine.
Meanwhile, Wheeljack has invented a "black hole machine" that will trap the Decepticons in another universe, ridding them of each other. During their next assault on the Autobot HQ, Wheeljack immediately sucks them in, but not before the Spychanger Scourge manages to steal Wheeljack's blueprints.
TO BE CONTINUED...