Scarlet Witch is human and her exact place of origin is largely unspecified. Scarlet Witch, also known as Wanda Maximoff, has the ability to change the probabilities of certain events happen. As such, she is essentially warping reality in a very real way. She is also capable of chaos magic, which can defeat enemies in very unpredictable ways.
Scarlet Witch has been a villain herself at different points. However, as a good guy, her enemies have included Apocalypse, Loci, and Magneto.