Romthule, the Virotyrants stride forth, spreading contagion and calamity in their dread wake. Some seek to make the black pilgrimage back to Old Earth, following the various River Networks such as those that criss-cross their way from world to world until finally, some few of them are believed to reach back to the still flowing waters of the cradleworld.
Driven by implacable ancestral wetware and the imperatives of hyper-evolved infections, the Virotyrants follow the rivers back through the gates, bringing death and disease to all the Dynastic Enclaves, Khemrid Crechecanals, and every other population, culture and civilization situated along the river banks.
But pestilences pass. Infections run their course. Immunity reasserts itself. Everything returns to normal. But what will happen when one of these things comes back among the worlds of far flung humanity? What will happen when a Virotyrant returns from their pilgrimage and they carry within them the core-codes of all life descended from the ancestors?