Loki/Wanda
Well. You were slightly possessed. By a lesser demon. We merely had to convince Mephisto to take Strange's soul as collateral for removal instead, while I shrouded myself invisible and used invisible ink to sign the parchment so that I also owned a stake in said soul, thus Mephisto could not claim it. It's more complicated than it sounds.
Since you're the same, but not the same, I do not think it would any longer. Not unless you go messing with another demonic entity. And that contract is binding since you are the only Wanda Maximoff in this universe.
Ah, magic. Chaos magic or a probability hex wouldn't be too common since it would be difficult to truly harness in full. I've studied in among the Aesir, Vanir, or Alfheim Elves. None have ever wielded such a power. That doesn't mean it can't be done though.
I am curious now, Wanda. Where did you hear of such a thing?