From the introduction:
"If you thought man’s past was dark, wait until you see his future.
Welcome to the Dark Horizons universe. The year is 2610, and the universe as you know it has changed. Mankind has conquered the the galaxy; technological breakthroughs such as the Core Implant, the quantum electrino drive, and cybergenetics have altered his way of life forever; and commerce with other species including Nomads, Cy-Gens, and the Valence -- has forever changed the way humanity defines itself. However, none of these changes has prepared mankind for the sudden appearance of the Irritus. Whether you participate in a Dark Horizons campaign as a player or as Gamemaster (GM), your actions during the game will help shape mankind’s future whether for better or for worse is up to you.