In the hope of taming the Great Rift that divides the galaxy in two, Archmagos Belisarius Cawl invites representatives from across the Imperium to the artificial world of Pontus Avernes. Confident he can convince them of his genius, he must secure their assistance in unlocking the secrets of the pylon network – significant structures built by an ancient race that he believes can stave off the pull of the warp. But among the attendees is an uninvited guest: Fabius Bile himself. The Pater Mutatis needs no validation of his genius and has his own agendas, the pursuit of which will bring about an epic confrontation of the galaxy's greatest scientific minds – and from which only one can emerge victorious.