IF

This takes place during Captain America: Civil War. Isabella Stark (Tony Stark’s daughter) was taken by HYDRA when she was thirteen. She’s seventeen now. She was taken because during The Battle of New York she touched the Tesseract. It should have killed her, but for some reason, it didn’t. This gave her powers. Given the fact the Tesseract contained the Space Stone, she could form portal’s to anywhere in space and move things with her mind. It also altered her appearance slightly. Her eyes, once a dull brown became a sharp, electric blue. Obviously, HYDRA found out about this and took her. No one has seen her since then. HYDRA made her into the perfect assassin. However, they did way more than what they did to Bucky (The Winter Soldier). Not only did they brainwash her, they somehow managed to get a mutants DNA (specifically, Mystique’s DNA) and altered Isabella’s own DNA with it. So, she can essentially mimic anyone as well. This story starts with a news alert, explaining how there’s been unexplained events including some key S.H.I.E.L.D agents ending up dead. Eventually, team cap and team iron man may have to reassemble if this escalates (which it will) The Avengers do NOT know that she was taken by HYDRA.