The Callosians constituted the original inhabitants of the world known as Callos.
Their civilization achieved a high level of refinement, built around a life dedicated to academic pursuits and philosophical inquiry. In the year 3 BBY, the forces of the Galactic Empire launched an assault on their planetary home, resulting in the complete annihilation of its ecological balance and making the planet incapable of supporting life. Those that survived the initial invasion were ultimately eliminated by the extremely cold conditions that characterized the planet's altered climate. A surprising number of Callosians who were off-world when the attack happened went against all reason and made their way back to their ruined home, seemingly with the intention of meeting their end there.