Back to Puella Magi Adfligo Systema.
Some time after the events of Rebellion, Madoka gets her memories and powers back and both she and Homura realize that neither of their universes (and thus, wishes) have worked out like they hoped. So instead, they send back a message to Madoka before she makes her wish in episode 12, prompting her to revise it and for Homura to abandon that timeline as another "failed loop". The resulting paradox erases both Goddess Madoka and Devil Homura from existence and resets the universe back to what it was beforehand, only with Sabrina added into the mix.
Sadly, Sabrina's true purpose is to fall and destroy (not save) the universe, which is also unfortunately Goddess Madoka and Devil Homura's plan. Her witch will do what they couldn't: Putting an end to the Magical Girl system (preventing it from existing in the first place), rewriting the universe and letting them all live as normal girls. Except for Sabrina herself, who will have never existed as she was the product of magic. And before the end, she will find this all out and will accept what she has to do in order to make a better world for everyone.
And The Stinger will be a retread of the first scene of the first episode, only with Sabrina being the new transfer student instead of Homura (who is already there). Madoka, Homura and Sayaka will all think they've seen her somewhere before.
The story takes place instead of Rebellion
, and Feathers is Devil Homura from an alternate timeline.
After all, Homura's consciousness moves from one timeline to another, why not Devil Homura's? She is somewhere "outside" of time, hence black feathers only falling in when Sabrina does things like try to create a barrier, or other things that lead back to a timeline where Madoka wishes away witches and Rebellion occurs. The reason why Feathers shows up as worse than Walpurgisnacht in Oriko's visions is because Rebel Homura still holds grudges and will mis-identify Sabrina as a witch or an obstacle and try to get rid her
, causing Sabrina to witch out or otherwise leading to a catastrophe.
Sabrina is a witch and the entire story has taken place in her labyrinth.
The earth has been purged of human life, and nobody except Sabrina is real. Sabrina is someone that Homura met and tried to make use of in one of her loops (Kyubey also only contracted with her because of Homura's influence), but she ended up being anything but and made things much worse
. It turns out that doomed timelines still exist after Homura abandons them, and Dedolere's delusional Power Fantasy
inside her barrier is to be a powerful hero, savior and exactly the opposite of who she was as a human. It explains why she has no human memories and why she's so protective of the girls (especially Mami)... because she failed them all.
Sabrina's original wish in unknown, but Dedolere's is to end grief... her own. Which will never happen. In other words, the entire story is a sad Deconstruction of OC roleplays, in that the real Sabrina was someone so useless that Homura didn't bother with her ever again after a single loop.
- Alternatively, at some point Sabrina will be compelled to think this is the case but it's not, because a witch could not understand (and thus replicate) The Power of Friendship.