A relentless legion of shadowy demons intent on annihilating every reality is invading our world and all alternate Earths. Standing in their way is the most formidable group of metahumans ever gathered. Yet, even the united strength of Superman, Batman, Wonder Woman, Green Lantern, and their superhero allies cannot halt the advance of this unstoppable force. What enigmatic power is propelling these demons? And how do the deeply hidden secrets of the Monitor and Supergirl endanger our final line of defense?