This Scarlet Witch fact is related to the creator, Stan Lee.
For Stan Lee, Scarlet Witch (along with Quicksilver) is one of his favorite characters.
Stan Lee said that the concept of both is an enemy, which is actually not too evil and can be loved by the reader. Therefore Stan Lee has a concept to make Maximoff brothers change from enemies to heroes, and join the Avengers.
It's called Scarlet Witch, Witch, but basically it's not a witch, it's just mutant.
Even so, he practices the way to use magic too, you know!
In the comics, he practiced with Agatha Harkness, one of the magicians in the world of Marvel comics. The power of his magic will be used to control his mutant power.
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