Magic is so terribly finicky.
Herridan Lionheart does not like the way his body works. Humans were not meant to be shackled to one form for their entire lives, he tells himself. Magic exists that can change that. However, he is neither too stupid to understand the principles of magical-biological interactions nor unwise enough to test his theories on himself. He also has enough overall power to operate more or less freely in the low-hero-density areas of the world, and is devious enough to get access to some very... Unique source materials. The most powerful magic-entwined biologies alive today are very promising test beds for his work.
Progress is rapid. But there's a lot of progress to be made. Most early experiments are miscarriages. The first one to be successfully born dies within the minute, of... Probably oxygen deprivation, is what he eventually decided. The fact that it set very vigorous fire to the medical unit before dying was a hint.
More experiments. He got good at preserving the surrogates, honed convincing them to volunteer to a science - he was having to move around too much to escape angry crowds, before. (It's not like the big hero teams were going to come down on his door. People like him were a dime a dozen in these parts of the world. For now.)
Now he could stay in one lab for years, try to see some of the modifications develop long enough to prove the concept. Herridan really does qualify as a genius... Some of the relatively conservative experiments worked perfectly - children born in his labs grew (slightly faster than normal) to adolescence and adulthood with regenerative blood, or subtle magesight, or fingernails with high concentrations of precious metal. (This is about when Herridan Lionheart started getting rich.)
He's almost legitimate now, backed by and backing up some tin-pot dictator. A veneer of authority to the place. He couldn't stop there, of course. With proper facilities his experiments could be more extreme, push the limits further. The Lycan program is promising, and ongoing. Project Unicorn meets dead end after dead end but it would be so revolutionary he keeps pouring resources into it. He quickly graduates from tin-pot dictator to somewhere in Mexico. That "accountant" is really good at his job...
One pair of children have wing-arm hybrids for upper limbs, a forehead crest of brightly colored feathers, and dully glowing eyes. Their magical properties are promising - flight, of course, despite the wing structure not having nearly enough lift or control for how well they perform at it. Kicking reflexes and a foot structure that seem to be meant for hunting. Overall strength and speed boosts that are rather pedestrian compared to some exotic effects he's managed, but intriguingly stable. Psychology mostly unaffected. Excellent results, exactly the sort of thing the program is looking for, if only he could replicate them.
The two star experiments have every physical need catered to and many more luxuries than most in these halls. Free time, a real teacher for literacy and numeracy tests, games and toys and better food and even a specially built open-air cage with perches and such for them to stretch their wings... And no friends or family or real freedom at all.