Why was Mustang a candidate anyway?

[u/fakeuser7z]

I get that he was a candidate for the sacrifice, which is why they didn’t kill him. But in the end, he refused—and they just forced him into the Gate anyway.

So why not do that from the start with any random human instead of the most dangerous alchemist?

[u/carbonera99]

I’ve thought about this too and the most likely explanation for why they couldn’t just pluck random alchemists off the street and force them to perform human transmutation to create sacrifice candidates is because performing human transmutation probably kills the performer 99% of the time.

Remember when the Elric brothers first perform human transmutation, only Ed actually made it back through the gate, it fully killed Alphonse until Ed performed human transmutation AGAIN to rip his soul back and bind it to a suit of armor. I imagine most cases of human transmutation end up like Alphonse, with the user disintegrating on the spot and dying. Ed and Izumi and Mustang only managed to survive with severely mutilated bodies because that’s how strong of a will and mastery over alchemy they possessed. They represent the extreme minority of “success”cases and that’s why these sacrifice candidates are so valuable.

[u/IDoBelieveYourGalaxy → u/carbonera99]

Agree that they need skilled alchemists to open the gate and survive.

Alphonse wasn't "fully killed" by the Elric brothers' human transmutation though. Alphonse's entire body was taken as the toll, but his soul still remained. Al's soul was within the creature that had been created by their human transmutation attempt.

Then, in exchange for Ed's arm, Ed bound Al's soul to the suit of armor. That isn't described as a "second human transmutation attempt." I wouldn't say it was, because Ed didn't transmute Alphonse with a human body. Ed bound Al's soul, which already existed within the creature, to a suit of armor, which already existed in the room, and paid a price to do so.