Twin girls who've been cursed with immortality. Seeing their families dies around them and all their friends as well, scarred them for life. Now they live a life in violence. One seeks to protect while the other destroys. They often fight each other.
In this picture she is showing power by staring right at what would be the camera. The mermaid, serena will dress like this as when she trains herself to be a warrior to fight her dad to save her town.