Welcome to the mind-blowing worlds of the Commonality Core - humankind`s most ancient and advanced civilization; a people of deep yet divergent cultures, riven by the shock of contact with new and rediscovered worlds. The Core Worlds are where humankind began - but now, after ten-thousand years or more, maybe they`re no longer human at all... Play Fringe Worlders experiencing the strangeness of the Core first-hand, or Core Worlders, sure of their superiority, until they leave their homes and are found wanting. Play planetary sentiences ruling whole worlds, ancient dynasties with plans crossing millennia, illegal xenomorphs fighting oppression and neglect in the forbidden substrates beneath the towering arcologies. A bright, bizarre, and thought-provoking milieu for your Mindjammer games, the Core Worlds Sourcebook features the history and background of the Core, including lavish maps, new genotypes, and strange subcultures.