The time opener

The evil hordes of the Wolochs are rampaging through space, and everywhere death and destruction follow. But despite the despair of some and the betrayal of others, Valerian, Laureline and a few other brave souls are resisting. They're hoping to use a mysterious artefact, the Time Opener, to banish the stones and bring back Earth. But what price must they pay to do so? And what sort of Earth will they get back if they succeed?