Amstron

The Amstrons were a species of intelligent hamsters. They wore humanoid armour. (COMIC: The Infinite Astronaut)

History
The Amstrons were once a peaceful race. Their galactic empire partnered with the J'arrodic Federation to create a wormhole to another universe. Two astronauts were sent through the wormhole, one an Amstron, the other a J'arrodic. The astronauts both died, but not before they sent the message, "It's the face of the creator", back to the Amstrons and J'arrodic.

The Amstrons argued with the J'arrodic over whether the creator looked like an Amstron or a J'arrodic. The argument led to a war. (COMIC: The Infinite Astronaut) Already when the First Doctor studied in the Time Lord Academy the war was known as the Eternal Dogfight and its origins had been forgotten. Amstrons were known to be one of the most intimidating and polite military organisations in the known galaxy. (COMIC: The Eternal Dogfight)

In 2015, Alice Obiefune resolved the long standing dispute between the two empires, which began peace negotiations. (COMIC: The Infinite Astronaut)

Circa the 38th century, (COMIC: Doctormania) an Amstron visited the Fluren Temporal Bazaar. (COMIC: Weapons of Past Destruction)

Undated events
The Eleventh Doctor had to save Rokhandi from the Amstrons twice in order to obtain a landing permit to the planet. (COMIC: The Friendly Place)

Behind the scenes
The reveal at the end of the comic story The Infinite Astronaut that Amstrons are actually sentient hamsters uncovered the in-joke of Amstrons describing themselves as being "of the Great Wheel" or simply "of the Wheel".