DaoistUqX3D7

Well they could be useful for ingredients for Alchemy (maybe toward Holy, recovery or other potions that help expend his affinity to light and permanent boosts or other things ...) or he coule steal their Lifeforce (and maybe keep it to use it later for a philosopher's stone they do live for a long while so they have a lot of it) and use them to practice Alchaestry. Or all of the above and more, he does have 4 of them that's quite a bit to use and maybe some leftovers for some good old homonculi. He doesn't have to send them to Azazel, they came to kill him he is protected politically by the Gremory family as the contracted magician of the Heiress, that way they don't tattle on his powers and put him more on the spotlight so that he have more time to Grind it's an open and shut case of Fallen going rogue, alternatively he send back one or two back for cookie points with Serafall and Azazel (he most likely will not care 'till he gets info about MC during the interrogation and will use the excuse of compensating him to study the interesting Human and his sacred gear) and says he killed the others during the fight.

+1