10 Disturbing Backstories Behind Doctor Who Characters

The Ood are a humanoid species the Doctor encountered on a number of occasions. When they were first seen, the Ood were shown to have a cable and sphere extending from their facial tentacles. This was used so they could speak, but it was also used to control them.

The Ood were enslaved and sold as property throughout the cosmos, which is something the Doctor wasn't especially appreciative of. Through his investigation, the Doctor learned that the Ood didn't always have the sphere coming from their tentacles, and instead, they possessed a second brain, called the hindbrain, which they held in their hand.

When they were enslaved, humans removed the hindbrain, which contained their memory and emotions. They were an intensely docile species, but that only made the easy to capture and enslave. It was revealed that while the individual Ood had two brains, they were connected to a gigantic Ood Brain.

This was the telepathic center of all the Ood, and it was likewise enslaved. The brain was an important part of Ood physiology, as they were all connected telepathically. Destroying the Ood Brain would have killed them all, and suppressing its mental faculties resulted in keeping the entire species docile and easily enslaved... for a time.