From the back of the book:
The Stars are Falling
Thousands of years have passed since Earth was lost and humanity fled to the stars. They colonised a new world but never escaped their enemy, the Rephaim. Civilisations have risen and fallen, and magic has brought us to the edge of destruction.
This is the Fourth Age
The Final Age of Humanity.
The stars are falling and the Kingdoms of Altais lie in ruin. As the blight of the Rephaim spreads slowly across the land, heroes search places long forgotten with sword and spell, hoping to restore the technology of the past.
Altas: Age of Ruin is a dystopian science fantasy roleplaying game focusing on the last struggle of humanity on an alien world.