Ood

The Ood are a benevolent alien race appearing in the British sci-fi television series Doctor Who. They are telepathic humanoids with a gestalt hive consciousness and are native to the frigid planet known as the Ood Sphere. Unfortunately for the Ood, their peaceful nature led to their race being enslaved by humanity following their discovery in the 39th century.

Biology
The Ood are a humanoid race with coleoid tentacles used for feeding purposes located on the lower portions of their faces. They lack vocal cords and instead speak via telepathy. They are also a long-lived race, though their approximate lifespan is unknown.

Ood possess two brains: a "forebrain" within their heads and a secondary "hindbrain" that is external. This hindbrain is carried by hand and is connected to the Ood's body via a tubular extension resembling an umbilical cord extending from the mouth. The hindbrain processed emotions and memories while the forebrain was responsible for higher thought processes and telepathic communication. Ood can survive without a hindbrain, but its removal will result in mental instability. When the Ood were enslaved by humanity, they had their hindbrains severed and replaced with cybernetic translation spheres that were connected to their central nervous systems and allowed them to communicate with their human owners.

Under normal circumstances the Ood were benign and harmless creatures. However, due to their brain structure they were susceptible to manipulation, as demonstrated by how easily the race was enslaved by humanity. More worryingly, their passive telepathy allowed them to be easily controlled and/or possessed by more powerful telepathic entities, such as the Beast.

Telepathic abilities
The Ood were originally a hive mind led by the Ood Brain, using their hindbrain to "sing" with each other. The colour of an Ood's eyes changed with the level of telepathic activity, normally glowing bright-red but turning to white when not connected to a hive mind. Humans, who only knew the Ood in their telepathy-disabled form, misinterpreted the presence of red eyes as a disease, known as "red-eye".

History
The Ood were a peaceful herd-race originally. In the 39th century, humanity discovered the Ood, enslaved them, and used them to perform menial tasks throughout the three galaxies of the Second Great and Bountiful Human Empire. The external hindbrain of the Ood was extracted by Ood Operations and replaced with their translator globes. With their connection to the Ood Brain severed, they followed the orders of humans. Ood Operations kept this procedure a secret from the rest of humanity, spreading the belief that the Ood were naturally servile and offered themselves for servitude.

By the 42nd century, it was claimed that every human had an Ood servant. They were generally barely even regarded as being alive, and were considered to be expendable. Despite this, an activist group, the Friends of the Ood lobbied for the cause of their freedom.

In 43K2.1, the Ood were being used for menial labour on Sanctuary Base 6 on Krop Tor. The Ood knew of prophecies regarding the Beast, which the Walker Expedition would later discover. The Beast possessed the Ood, and made them into his "Legion" in order to besiege the human party of the expedition. They were defeated when Danny Bartock, the expedition member in charge of them, broadcast a telepathic flare which reduced their field to Basic Zero. This created a "brainstorm" which caused them to collapse. However, their telepathic field began to reassert itself after a time. When the Tenth Doctor broke the gravity field that kept Krop Tor in orbit around the black hole K37 Gem 5, the Doctor was only able to make a single trip in the TARDIS to rescue Ida Scott from suffocation; he was unable to save any of the Ood on the base, who had just been freed of the Beast's control. All perished but were given posthumous honours.

In 4126, the Tenth Doctor and Donna Noble visited the Ood Sphere by happenstance. They found Ood Operations, and decided to learn the origins of the Ood and what or who had turned them into a race of slaves. At the same time, the "red-eye" disease was becoming more and more common. They discovered that the disease was caused by the Ood Brain's subconscious reasserting itself over the Ood thanks to the efforts of a member of "Friends of the Ood" who had infiltrated the company secretly.

Ood Operations' head, Klineman Halpen was unwillingly transformed into an Ood as a culmination of him taking hair tonic deliberately contaminated by his own Ood servant. The Doctor deactivated the field that was suppressing the Ood Brain's telepathy and it sent out a song that was heard by everyone across the three galaxies. Humanity, now knowing the truth about their Ood slaves, returned them to the Ood Sphere, where they were set free and allowed to live in peace.