Even the Wizards Must Pay their Due 
is a quite popular and thoroughly controversial Fullmetal Alchemist crossover with Harry Potter. According to Word of God it was written because he been reading Penance and when he got to the bit with the boggart and Dumbledore snooping, his mental Ed started kicking and screaming about how that would never work, since Father wanted those who had been to the Gate because they carried a bit of the gate with them. Then it grew.
The story begins with Dumbledore using Legilimency on Ed, as has been done before, but unlike in other stories, this one had a rather different result. A result named Truth. The immediate reaction of the Elric brothers to Dumbledore's action is to leave mayhem behind them and take the child he planned to use home with them. And from there the story unfolds...
Examples
- Adaptational Badass: Xiao Mei
- Action Mom: Izumi adopted Harry, thus making her a mother.
- Amplified Animal Aptitude: Xiao Mei
- Alchemy Is Magic: Inverted. Magic is Alchemy, and the power comes from the life of the wizard.
- Atlantis: Amestris is a country on Earth in this story. But what? that's not possible? What about all the neighboring countries? Cavy had a solution to the problem. The Xerxesians got tired of being bothered by would be conquerors and people begging help, and hid the whole continent.
- Attack Reflector: Dumbledore tried to kill Ling. Greed backhanded the spell away and it took of the trailing end off of Dumbledore's beard.
- Badass Boast: Truth gets several, and Mustang gets one as well.
- Berserk Button: As in the manga, Ed hates being called short. Mustang keeps score of how often he can hit this one.
- Best Friends-in-Law: Ed and Ling are well on their way to becoming this, much to Ed's distaste.
- Big Friendly Dog: Actually big friendly Shapeshifter Mode Locked dog Animagus.
- Big Brother Instinct: to Al, as in canon, and to Harry.
- Blocking Stops All Damage: Only when Greeling does it.
- Cosmic Plaything: Truth is a busy little deity, nudging Ed into position to take down the wizards. Even more than that, a side story revealed that Ed was specifically created to be this. At least Ed gets a heads up fifty percent of the time.
- Curb-Stomp Battle: The Amestrians to the wizards. Six wizards vs half the World of Badass that is the FMA cast? That was probably overkill.
- Equivalent Exchange: This is a Fullmetal Alchemist story.
- Deadpan Snarker: Ed and Mustang.
- Gate of Truth: This is a Fullmetal Alchemist fanfiction. A bit more interactive that the usual examples of this, Ed gets frustrated by it's continued laughter.
- Humiliation Conga: The wizards are dancing to Truth's tune on this one.
- Mind Rape: Dumbledore trying this kicked off the plot. Trying it again later resulted in his death. Snape and Moody try it too, with similar results to the first time.
- Samus Is a Girl: The Phoenix is nether male nor Dumbledore's. She's Truth's, but she'll stay with Ed.
- The Prophecy: Subverted. There is one, but it comes up near the end, and consists of Doomy Dooms of Doom.
- The Omniscient: Truth.
- The Dog Was the Mastermind: In this case it was The Phoenix, by Truth's command.
- Wacky Marriage Proposal: It's implied, but not quite stated, that Ed got down on one knee and gave Winry an engraved wrench suitable for a Wrench Wench, while blurting out the canon Equivalent Exchange.
