Gods of Mars — Graham McNeill

Beyond the edges of the galaxy, Archmagos Kotov's great voyage is over. He has achieved his goal - to find the resting place of the long-lost Vettius Telok. But Telok yet lives, and as the brave explorators of Kotov's fleet marvel at the wonders laid before them, darker plans unfold. As reality itself is threatened by impossible technologies from the dawn of time, it falls to a small group of heroes to thwart an insane plan that could see the entire universe annihilated.