Origins of the Immortal Races

The Ancient Makers sculpted the world, then made the first life. Their Firstborn were immortal and undying, their growth unchecked by any limitations. Some of the Makers gloried in their children, anticipating the results of unrestrained evolution. Others feared the doom of all things, all creation devoured by life uninhibited.
The Firstborn were brought to war, but their Makers had fashioned them too well. They could not be killed, so instead they were banished, or imprisoned, or divided. From the division of the Firstborn, the Makers fashioned new creations.
From their immortality and undying spirit, came the immaculate Celestials. From their essence, raw power realized, came the mercurial Elementals. From their vicious will to live, their ambition for growth, came the dauntless Infernals. From their flesh and blood, polluted by potential, came the beastly Primals.
The protean Primals, tainted by the dark blood inherited from the Firstborn, were cast into the darkness between the stars, or entombed in the earth to breed monsters. The loyal Celestials served the Makers as champions, enforcers, and companions, watching over their further creations. The Elementals, inconstant and unreliable, were woven into the essence of the world, to slumber until the need to cull incautious life would awaken them. The zealous Infernals, ever-desirous of glory and advancement, served the Makers as hunting hounds, battling the vermin-refuse of cycles long past.
In time, their service became unnecessary, and the Infernals were granted custodianship over the realm of prisons fashioned by the Makers, the Dungeon Dimensions. For eternities they watched over their charges, but grew listless, their evolution stagnating. They sought to leave their station, but found themselves imprisoned along with their charges. Betrayed by the Makers, who feared them as they had the Firstborn.
The Celestials still guard their Makers throne-realms. Ever-watchful. Ever-loyal. Ever-fearful.
The Elementals sleep.
The Primals wait.