So, one: There was a leak mentioning a "Dark Star Guardian" skinline in contrast with Regular Star Guardians featuring a DSG Syndra (in SG lore, she was very...untrustworthy)
Also, this just reminded me of "Panty and Stocking with Garterbelt" which is an anime that makes fun of Western Cartoons (watch it for no other reason than all the pop culture references and to inevitably realize every cussword spoken is now just random sound effects in the background)
Oh, and before I forget, that art is beautiful. My only critique is that, unfortunately, I can't see Morg like that properly Not because she's evil, but because she is "fallen".
I can tell you put detail and thought cause Kayle is floating, and Morg is obviously using her feet, but there is no contrast otherwise. I'm thinking that you give Morg some dark colors which naturally contrast Kayle. I see a bit of purple on her corset, but that should honestly go for the wings or just overall any piece of white that you have on the piece.
Think of it like how for Xayah and Rakan, Xayah has dark colors while Rakan has a brighter contrast. Any new skins they get together will definitely play a "compare contrast" imagery, but this doesn't have that. It's the same visual aesthetic theme that doesn't tone shift for the individual. Once again, the only contrast there is Kayle floating and Morg standing.