Where to go from here?

There is a girl born with the mark of the chosen along with 9 others forming two team of 5 of good and evil. This fight is locked in a loop and restarts ever few hundred years. The chosen are born with special gifts parallel to their evil/good counter parts and are 10-20 times stronger than normal humans. Evil is winning with 3 members of good already dead. The girl has a twin sister who isn't special, isn't a chosen. On the day of her execution, her sister try to help save her but was beaten to a bloody pulp. As the sister lay there, watching her meet her doom, the sister cried out for them to stop as they took the final strike at her and then something unexpected happened. The crystal charm the sister had as a necklace began to glow as bright as a shooting star. The crystal then merges with the sister and then boom, the sister erupts with power, destroying everything around the sister. Creatures across the universe turns their gaze towards Earth as they sense an enormous power. The sister is transformed into a pure energy being that resembles an angel. The sister is completely out of control and destroys anything in her path. They have never witness powers like this before. The sister is like over a gazillion time more powerful than they are. And this is where the loop breaks. They've been locked into that loop for so long, that's all they've ever known. Everything is about to change. But first someone needs to stop the twin sister from destroying the Earth.