Arcateenian

The Arcateenians were a race of humanoids who hailed from Arcateen V.

Biology
Arcateenians took on a humanoid form. In order to maintain their shape when on a planet with a stronger gravitational field of their own, they required large amounts of energy. Their main form was that of a translucent humanoid, with their internal structure seen faintly through their skin. Their hair was made up of tendrils on the top of their heads and on their backs. They had five long, slender fingers and a blue tint to their skin. Some Arcateenians had wings, which enabled them to fly.

One notable Arcateenian, named Mary, had the abilities of super-speed, strength, telepathy, and could inhabit the body of a human for nearly 200 years, all while keeping the body young.

Technology
The Arcateenians utilised numerous methods of faster-than-light travel. They had different types of spacecraft, including large white 'hearses' which carried a suspended animation chamber and two battery packs. During the 1800s, they also used smaller transporters that were handheld, used dark matter, and even teleport the user. The Arcateenians created pendants to communicate telepathically with each other, as well as possessing superluminal communications technology.

Culture
As stated by Mary, who was an Arcateenian criminal, she found her fellow Arcateenians to be savage. They forced each other to worship in large temples stated to be "the size of cities", as well as having execution squads roam everywhere on the streets and enforcing death penalties for every crime. It was later implied by Captain Jack Harkness that Mary could have invented those details to create the impression that she had been oppressed. Arcateenians had a tradition of burying their defeated foes on a "barren, savage outpost".

Arcateenians chose to communicate by using telepathic signals picked up by pendants, yet they still had a written language.

History
During the early 1800s, Mary, an Arcateenian criminal, was sent to Earth alongside her jailer, whom she then murdered. She then took over the body of a human passing by. Staying on Earth for nearly 200 years, Mary kept herself alive by feeding on the hearts of other humans. According to her, during that time, Arcateen V was run by an oppressive government who forced worship and exiled prisoners like herself.

By the 20th Century, the Arcateenians liberated the planet Tivoli from the forces of the Fisher King, much to the dismay of the native Tivolians, who started annoying the Arcateenians so much that they enslaved the Tivolians themselves by the year 1980. The Arcateenians gave Albar Prentis, a Tivolian funeral director, a spaceship to help him on his mission to bury the Fisher King on the backwater planet of Earth.

In the 21st Century, it appeared that there was a benevolent government on Arcateen V, and peaceful poets from it would travel to other star systems with their poetry. One star poet encountered Sarah Jane Smith one night, and gave her a superluminal communications device before flying back into space.

Later that year, the Torchwood team did an excavation, and found an Arcateenian prison transport. Mary, who was originally imprisoned within it, tried to infiltrate the Torchwood base to reclaim it, by manipulating Toshiko Sato to do so. She succeeded, but unfortunately for her, Captain Jack Harkness had reprogrammed it, causing it to teleport itself, and Mary, to the Sun.