Changing the past

Vandal Savage. An evil dictator blessed with immortality. He has achieved what no one in human history ever has. He has conquered the entire planet. A superhero team ( Arrow, the Flash, White canary, Steel, the Atom and Supergirl ) needs to travel back in time, to prevent Vandal from killing Chloe Beale. They need to change the past to save Beca and Chloe's future.