To put it succinctly: Wanda made a Faustian deal with the devil in order to be able to resurrect Vision and create the pretend life she is leading.

Alternate “Go with me” theory here. What if everything you said was true; about the Faustian deal, the extension of her powers, the kids, etc. But...instead of Mephisto, who you have to admit is a pretty obscure Marvel character, especially when we’re talking about just the MCU, it’s a character we all love to hate....


Loki! Think about it. We know he had a flair for the dramatic. Literally, with him posing as Odin and forcing his people to reenact his story. We know he craves attention and most importantly chaos. He LOVES manipulating people the more powerful the better. The closest he came to destroying the Avengers wasn’t with the Chitauri but when he was subtly manipulating and maneuvering each member against one another before the invasion. Also Loki was before Wanda, Vision, and Pietro came around so they have never faced him so would more likely fall for his tricks. We know the more straight up evil Loki (before his redemption arc) is the one running around with the space stone. And he looks pretty comfortable sporting devil like horns. He also conveniently has his own show coming up with which we have no idea what it’s about. He also said several times in various movies and comic books that he’s always wanted to live in the suburbs and raise twin boys. (Ok I made that last part up). As the saying goes, why Mephisto when you can Loki...or something like that.
The only thing is that he’s in the wrong part of the timeline. But that could easily be fixed.
It’s just a thought anyways.