Mondas

Classic series (1963–1996)

The Cybermen first appear in the serial The Tenth Planet in 1966, set in 1986. This story explains how, millions of years ago, Earth had a twin planet known as Mondas that was knocked out of solar orbit and drifted into deep space. The Mondasians, already far in advance of Earth's technology and fearful for their race's survival, replaced most of their bodies with cybernetic parts. Having eventually removed all emotion from their brains (to maintain their sanity), the natives installed a drive propulsion system to pilot the planet itself through space. As the original race was limited in numbers and were continually being depleted, the Mondasians – now Cybermen – became a race of conquerors who reproduced by forcibly changing other organic beings into Cybermen. The First Doctor (William Hartnell) opposes these Cybermen when they attempt to drain the Earth's energy to make way for Mondas' return to the Solar System; in this encounter, Mondas absorbs too much energy from Earth, destroying it and all Cybermen on Earth. The adventure takes its physical toll on the Doctor, forcing him to regenerate for the first time, becoming the Second Doctor (Patrick Troughton).