Roboute Guilliman and his corrupted brother Mortarion converge on Iax, a once-thriving Imperial world now teetering toward oblivion. The Lord of Death executes his grand design—leveraging the planet as a gateway to drag all of Ultramar into the warp's embrace. As Guilliman fights to save his realm, Mortarion unleashes the Godblight, a plague forged in Nurgle's Cauldron with the singular purpose of annihilating an Emperor's son. Primarchs wage war across Iax's devastated terrain. The gods themselves clash. The galaxy trembles on the precipice of ruin. When the dust settles on this final chapter of the Plague War, the victor's triumph will reshape the cosmos forever. By Guy Haley.

Guilliman races to defend his domain as Mortarion deploys his ultimate weapon—the Godblight, a pestilence born from Nurgle's darkest forge. This plague carries the power to fell even an Emperor's progeny, turning the tide of their fratricidal struggle and threatening everything the Ultramarines hold sacred.

Two demigods collide amid Iax's scorched wastelands. Divine forces descend into open conflict. Reality itself hangs suspended between annihilation and salvation. In the warp's depths, something ancient awakens. One certainty remains—whichever Primarch emerges victorious from this final Plague War confrontation will alter the fate of galaxies for all time to come.

Written by Guy Haley