Out of desperation, Dumbledore uses a combination of dark and chaos magic to summon someone who has the knowledge on how to defeat Voldemort, only what what he got wasn't expected. Self-insert story. There is also swearing.
A young man is brought from his world, to a world he believed to be fictional. Little did he know, his friends came along for the ride. WARNING: Rated M for swearing.
Harry Potter doesn't exist. Voldemort was still defeated. A new prophecy is made, forcing a boy out of his world and into theirs. Self-insert. NOT a Deus Ex Machina.