Belisarius Cawl's long-conceived strategy to secure the Attilan Gap and establish a reliable passage into Imperium Nihilus reaches a critical juncture in this novel by Guy Haley. With Primarch Roboute Guilliman stranded beyond the Great Rift, the window for success narrows as Cawl races against mounting pressure to execute his ambitious design and reconnect the fractured Imperium before circumstances render his efforts obsolete.

To complete his magnum opus, Cawl must obtain critical control codes hidden within an ancient Necron vault positioned at the precipice of a black hole's event horizon. Recognizing the impossibility of solo achievement, he assembles a coalition of Adeptus Mechanicus operatives to mount the expedition. However, as success draws within reach, his activities attract the attention of darker forces—specifically Vashtorr the Arkifane—and Cawl soon learns that drawing the gaze of such malevolent entities carries consequences far beyond his calculations.