Cyclops

A Cyclops (plural Cyclopes) was a giant creature in Greek mythology with only one eye in the middle of its forehead.

The Cyclopes' home planet was destroyed in a war. The only survivors of the war travelled to Earth, where they began attacking the humans there, believing them to be their enemy. The Twelfth Doctor and Clara Oswald met the surviving Cyclopes in ancient Greece. Fetching his sub-conscious reading reality device from the TARDIS, he learned of the Cyclopes' plight. Using the device, he changed a few things in their sub-conscious, making them vegetarian to calm their hostility towards the humans. Upon Clara's suggestion, the Cyclopes moved to some nearby hills to live in peace. (COMIC: Doctor on the Menu)

Circa 500 BC, the Eleventh Doctor, Amy Pond and Rory Williams encountered Cyclopes on a Mediterranean island. (COMIC: Island of the Cyclopes)

In 410 BC, a Cyclops was one of the creatures brought to life by Zeus to punish the people of Athens. It was later destroyed by the Doctor. (COMIC: The Chains of Olympus)

In 2007, Torchwood Three dealt with a Cyclops in Pontprennau. (PROSE: Another Life)

The First Doctor encountered a cyclops named Fo on the planet Rhoos. (PROSE: The Playthings of Fo)

A Cyclops was one of the attractions at the Ancient Worlds theme park on Dewyn. It came under the control of a Chiffala and was used to attack guests attending the park. (COMIC: Minor Trouble / Inhuman Sacrifice / Crimes and Punishment)

Behind the scenes

 * According to The Brilliant Book 2012, a book that contains non-narrative based information, in River Song's World Cyclops were a pest in London, alongside unicorns and Satyrs. (REF: The Brilliant Book 2012)