It's the commissioner's OC, Serena, a human turned angel of Flight Goldnight. Her spark ignited and she went full Boros when Brisela happened. Canonically she got big tiddy but no dick. Also has a dominant streak, but is pretty vanilla otherwise. She's got a fair bit of commissioned art, although a lot isn't futa.
Presumably she's fucking Nahiri like Nahiri fucked Innistrad.