The Old Ones were an ancient and immensely powerful reptilian species, believed to have been the first masters of the galaxy in an age unimaginably distant. Masters of biological engineering and of the Warp itself, they wielded a command over life and space that no later race has come close to equalling.
It is thought that the Old Ones seeded countless younger species across the stars, engineering new life to serve their purposes. Among their supposed creations are the ancestors of the Aeldari, the brutal warrior-race that would become the Orks, and many others besides, each shaped for a role in a galaxy the Old Ones ruled through mastery of psychic gateways that spanned the void.
Their dominion ended in cataclysm. When the soulless Necrons and their star-god masters rose against them, the Old Ones were drawn into the vast conflict remembered as the War in Heaven. Though they created warrior-races to fight in their stead, they were ultimately overwhelmed, and the ruin unleashed in that war tore open the barriers between reality and the Warp. The Old Ones vanished, whether destroyed utterly or fled beyond knowing, leaving only their scattered creations and the wreckage of a galaxy that has never truly recovered.