Avarrach was once home to a bustling technologically advanced civilization. Without magic, the people of Avarrach turned to technology, making leaps and bounds in their advancement and the ways of magic fell by the wayside. Some of the greatest developments of their society included advanced cybernetic implants, nanotechnology, and a worldwide network that could connect anyone/anything from anywhere on the planet. But these things became their downfall when they sought the one thing they did not have: immortality.
One man was in love with Avarrach's Aleta. Keenly aware of her immortality and his own mortality, he sought to use technology to extend his own lifespan. To do so, he developed a nanotechnology to grant people immortality. However, this technology quickly took a horrible turn: the nanobots decided that flesh degraded too quickly, and that the best way to preserve a human body forever was to turn it into a machine. All across the world these nanobots began converting the flesh and organs of their hosts into metal machines, effectively killing every host from the inside out, turning them into "Zomborgs." Once dead, the host no longer provided life energy with which to power the nanobots, causing them seek new sources of energy. The nanobots connect over the network that once connected the humans, and sought out every last form of life on Avarrach until nothing remained. Unable to continue to power themselves, the nanobots (known as the Virus of Avarrach) went into a low power sleep mode.
The virus lay dormant until the rifts opened. Detecting new sources of life, the Virus reactivated itself and began to spread inexorably to the other worlds. Lacking sentience or strategy, the Sleepers merely strode forwards, an unstoppable, immortal force.
The arrival of the Overseers led to the near complete extermination of the Sleepers. Furthermore, the Genesis Industries have developed a cure for the virus, likewise neutralizing their threat. Although it remains incredibly difficult to fully wipe out the Virus, never again will the Avarrachian plague threaten the planes.