Why would they torture Lewellyn while he was a kid? What's Fawkes grand purpose?

it said it was “medical research.” lewellyn has that condition they mentioned thats why everyone treats him as a dog, so they were trying to make a “dog” that was completely loyal and obedient they could use. thats also why they used shavonne bc he was the only person lewellyn listened and didnt react aggressively to

Out of all the people, why does it have to be Lewellyn? Is his blood different? The dog is just an excuse to do whatever they want with him.