True Dark — Niall Teasdale

Twilight is missing. Her darkest personality has taken control, and no one knows where she is or what she might do. Across the globe, the cosmic energy pulse from two dying spaceships has unleashed a new wave of Ultrahumans, often stronger than has ever been seen before. In America, a hero thought lost returns, but with him comes a danger everyone thought had died beneath the ruins of New York. Cygnus, the Guardian of Earth, has her work cut out for her if she's ever to bring her lost friend home.