She has just become powerful beyond measure. Jean Grey, the psychokinetic, telepathic superhero from the X-Men franchise has gone rogue and tapped into her innermost recesses to find power that she can't control. Portrayed by Game Of Thrones' Sophie Turner, Jean Grey has become the Dark Phoenix who will stop at nothing - not even if it means having to eliminate everyone, including the other X-Men. 

The start of the trailer shows Jean Grey rendered helpless by the power she possesses that seems to bring harm to the people she cares about. Next, she's seen throwing Mystique, played by Jennifer Lawrence, into the air. But it does not show what happens of Mystique; is she killed by Dark Phoenix?