There is a massive increase in the number of humans born with psychic powers around this time. Many of these new psykers lack the mental discipline to successfully make use of their power and are possessed by daemonic entities of the Warp, unleashing untold destruction on their homeworlds. Many people on worlds where these rogue psykers have appeared began to treat all psykers as pariahs who should be be immediately executed. The term "witch" comes back into vogue in the human language that serves as the precursor to Low Gothic to refer to those who manifest psychic powers. Terra and all of its interstellar colonies are cut off from interstellar travel and communication by the start of massive, galaxy-wide Warp Storms. This isolation over the next 5,000 standard years interacts with the genetic modifications and simple adaptions to local environmental conditions to create the first Abhuman sub-species of the human race. Civil wars, plagues, daemonic possessions, persecutions and other terrible forms of strife consume many of the worlds of Man. A complete understanding of the knowledge once contained within the Standard Template Construct database available on every human colony planet is lost as is a complete copy of that database itself, once a collection of the most advanced human technologies developed over the last 25 millennia. This 5,000-year-long period of violence, fear and technological regression becomes known as the Age of Strife or "Old Night" to later Imperial historians. Human worlds throughout the galaxy are isolated by Warp Storms of terrible ferocity. A disastrous age of suspicion and dread begins as internecine conflict tears human civilisation apart. Fear and superstition lead to a regression in Mankind's mastery of science and many technological marvels of the previous age are lost to paranoia and war. Aliens and daemons alike prey on humanity's vulnerability, and although many planets are subjugated or lost, the surviving Knight Worlds continue to stand firm through this turbulent time -- however, none do so without earning scars that linger to this day.
Horiax Treatise Penned
The ancient Horiax Treatise, a rare scrap of information left from the Age of Strife, mentions the use of sophisticated genetic alteration techniques now lost to Mankind.
The depravity of the ancient Eldar empire plumbs terrible new depths. Cults of pleasure and pain flourish in the hidden reaches of the Webway, and even the core homeworlds of Eldar society become obsessed with the pursuit of ever-greater acts of excess. As the lines blur between simple sensation-seeking and the outright pursuit of evil among the Eldar of this time, a new spiritual entity begins to take shape within the swirlign currents of the Immaterium.