An enormous asteroid is on a collision course with Earth. Its impact will obliterate every one and everything on the planet, leaving the world a spinning, desolate husk. Some have known about the Doomsday Asteroid for sometime now. In fact, as a member of Odyssey Prime - a clandestine project created to prolong human life - it's your job to save humanity from extinction. Fortunately, Odyssey Prime has constructed mysterious portal devices. With them, your Odyssey teams can search for a final evacuation of the world and its inhabitants. At the same time, your Dam Con teams have to keep a lid on things at home. Odyssey Prime is strictly need-to-know. Panic in the streets only makes a nearly impossible job that much tougher! Odyssey Prime is a d20 Modern campaign setting of interdimensional/planetary adventures with the survival of the human race in the balance. It is a meta-game allowing seamless integration of any published setting, or any world of your own creation. The Odyssey Prime Corebook includes: a detailed background and history for the Odyssey Prime world; two campaign style choices: modern-day conspiracy and intrigue or high-tech dimensional exploration; detailed character information and new advanced classes; new skills and feats; new weapons, equipment, and vehicles; new rules to be used in any d20 Modern game, including a dramatic roll and alternate award systems; numerous adventure seeds, suggested worlds to explore, and a ready-to-run mission to get players started; and conversion notes to play Odyssey Prime using the Unisystem.