Elizabeth Olsen is the Scarlet Witch
Fun fact: Wanda Maximoff (Scarlet Witch) is a fascinating mutant with some serious family issues. Her father is Magneto, she is sister to Quicksilver and Polaris, and is the mother of Wiccan and Speed. Her mutant powers include probability manipulating & reality warping. She is responsible for the mutant catastrophe "M-Day". You may have heard the famous line "No more mutants". Those are the words she spoke when her father killed her brother Quicksilver. These three words, these little tiny words changed the entire marvel universe. With her reality warping powers those words caused 90% of the mutant population to lose their powers. It isn't until many years later when the Phoenix Force (cosmic universal power), came back to Earth and was subsequently defeated, that new mutants began to manifest powers once again. She'll be featured in the upcoming movie Avengers 2: Age of Ultron. SPOILERS!!!!!! Wanda was still very much hated by many mutants up until recently, especially by rogue. When Rogue suspects that Wanda is betraying the mutant race again she decides to kill her, and as far as we currently know, she is legitimately dead. Bonus Fun fact: Rogue killed her with Wolverine's bone claws that she borrowed. Gnarly.