Evil thought, but in the demon angel au, Sann and Albus require human meat to not 1, starve 2. Go crazy in hunger. So what if they found an immortal human?
Sann’s healing powers aren’t as great as they once were, he would pass out healing a broken bone, but if they found an immortal human that regenerates?
I would love to see them struggle deciding what to do. Like in scenario A, the immortal human is cursed, they can’t help it nor control it. So they’re obviously surprised to find the human they just hunted down up and running again. So after the second time, they keep them close to observe and verify they’re in fact, immortal. The human thinks is a curse they gave them, when it’s definitely another demon they pissed. So what if they choose to not torture the poor thing further, exactly like when they were with the butcher, who harvested their horns and feathers?
Or scenario B. Where the human is insane, so they think they’re keeping the demons satisfied in exchange of immortality with their “offerings”. They think they gave them kind of a blessing. After a few months they get used to pain, and they have two demons as allies that defend their town because that’s where their food is! Win win! What’s chopping up a few limbs every once in a while against that?
Or scenario C. Human is terrified of the demon that hold them captive and torture them by regenerating them and then chopping them off. They’re terrified in their little hole in the ground the white demon keeps them on. But they almost die, or maybe they did, of a heart attack when they see another one. The other one has wings and big horns. But somehow, they’re not pleased to find the demon kept food to itself and start fighting when the winged demon tries to take them out of the hole. When they succeed, the white demon snatches them away and proceed to chop one of their fingers, tugging on their hand for the other demon to watch how the flesh and bone regrow.
The human’s knees give out when the winged demon makes a weird expression. The human panics, thinking it will see them as food too. It will definitely try to snatch them for itself. They kinda pass out in their fear, but it’s not like being conscious would have made them understand the seething anger the winged demon has when it attacks the white one. They wouldn’t understand how they scream at each other about how wrong what Albus did is. How he acted like the humans to keep them fed and how sick Sann was that he had not questioned the source of his food, suddenly too frequent to be normal.
I wanna imagine a Sann who is so, so pissed off at Albus, he pushes him into the hole and keeps him trapped there. Waiting for the human to wake up so Albus can erase their memories and get them back to a human village that’s safe, while making sure Albus understands Sann is not taking him out or healing his broken leg and ribs until he concedes to his terms.