According to the "Official Doctor Who Annual 2007", the Ood live on a planet in the Horsehead Nebula, where they were governed by a Hive Mind that was destroyed by human colonists. The BBC-authorised book "Doctor Who: Creatures and Demons" elaborates that the Ood came from the Ood Sphere. The Ood Sphere is close to the Sense Sphere planet, home to the Sensorites, who share a mental and physical similarity with the Ood. Without a hive mind, the Ood offered themselves to the human colonists and became a slave race.