Something that not even Terra's top geneticists had anticipated. From the beginning, the primarchs were noted for their supposed inability to produce biological offspring, for reasons ranging from their colossal size to a lack of carnal desires, which was even inherited by the Adeptus Astartes, the Space Marines. An event that shook the foundations of established beliefs about the complicated biology of a primarch.

Primarch Vulkan had had a biological descendant, naturally, like any human in this galaxy

There had been an attempt to keep the news from spreading too far when the event happened, but in the Imperium, news traveled at the speed of light, and in just a couple of months, most of the Imperium already knew about it. The celebrations of the civilian population lasted for days, from Terra to Nocturne, celebrating the arrival of a primarch's descendant, and one as beloved as Vulkan. Perhaps it was the beginning of a new age of splendor for Mankind

That was six years ago

In the present, the Great Crusade is drawing to a close, the Battle of Ullanor ended with a victory of Mankind, and the Primarch Horus Lupercal was crowned Warmaster. The Emperor of Mankind has retreated to the Imperial Palace on Terra, for reasons unknown to all but his Adeptus Custodes and Malcador the Sigillite himself.

In the corridors of the Primarch's flagship, The Eternal Flame, the footsteps of the giant Lord of Drakes, Primarch Vulkan, could be heard