At some point in the distant past, the Earth had a twin called Mondas. It was identical to Earth in every way, including the evolution of a dominant humanoid race. Mondas had an erratic orbit, however, which caused it to be thrown out into deep space. The inhabitants had more advanced technology that that of their Earth cousins. Forced to endure the bleak conditions of their peripatetic existence, they realised that their race would soon die out. They therefore resorted to surgical techniques to survive. They replaced their limbs and organs of flesh, blood and bone with those of metal and plastic. To cope with their new life, the Mondasians also decided to carry out brain surgery - removing the emotions of pain and fear. Soon all other emotions were deemed weaknesses and were removed, making them creatures of pure logic. The Cybermen were born.
In appearance, they were all tall, with heart and lung functions built into a large chest unit. Their faces were covered by a surgical stocking material, in which the eyes and mouth were set - giving them a skull-like appearance. Their limbs had hydraulic attachments for greater strength. As Mondas was travelling far from any sun, they had a powerful lamp on the top of the headpiece, attached to the skull with thick handles. Their hands still looked human, though they had greater power. They carried an energy weapon beneath the chest unit.
In the year 1986, Mondas returned to the Solar System - guided there by a massive propulsion unit. Needing energy, the planet began to absorb that of the Earth. The Doctor, along with his companions Ben and Polly, was present at this time, having arrived outside Snowcap base - a space monitoring station at the South Pole. The Doctor recognised the new planet as Mondas, and warned the base personnel that they could expect visitors from it. The Cybermen arrived nearby and took over the complex. The power drain caused the destruction of the spaceship which they were monitoring. The Cybermen, some of whom had names, announced that the people of Earth would be taken to Mondas and be converted to become just as they were. They saw this as a good thing - removing despair and pain. The scout party was destroyed using their own weapons, and another squad met the same fate before they could reach the base. However, the Cybermen then invaded the planet in force. The Doctor realised that Mondas was absorbing too much energy, and would soon destroy itself - so urged patience. However, base commander General Cutler intended to launch the powerful Z-Bomb at the planet - even though it might wipe out much of the Earth as well. Cutler was killed by the Cybermen when they retook the base, but the Doctor's prediction came true. The Cybermen were unable to halt the power drain, and Mondas began to break up. They had not had time to transfer their power source down to Earth, and so the Cybermen perished with their planet.
These Cybermen had a weakness when it came to exposure to radiation.
Many years later, the TARDIS materialised in a massive colony ship which was stranded on the edge of a black hole. Gravitational distortion from the black hole meant that time moved differently at either end of the ship - minutes at the front lasting years at the rear. Crew sent to the rear of the vessel had become generations of people. A whole city was created, which the Master attempted to rule over when his TARDIS arrived there. He was overthrown, and hid in the city hospital in disguise. The colony ship was Mondasian, and evolution took the same path here. The colonists began the same process of replacing limbs and organs, and of removing their emotions. The Doctor's companion Bill Potts had been shot through the heart by one of the crew, and was taken down to the rear of the ship. Here she had an electronic heart installed. She befriended a man named Mr Razor, who turned out to be the disguised Master. He caused her to be converted into a full Cyberman, although her love for the Doctor allowed her some emotional freedom.
The Cybermen were compelled to break out of the rear sections of the ship and work their way forward, in order to convert others. The Doctor decided to make a stand to help those colonists who had established themselves in one of the upper levels. He tried to get Missy and the Master to help him. He refused, whilst she was on the point of joining him when she was killed by her earlier incarnation. The Cybermen evolved as they moved through the ship, so that the Mondasian design of Cyberman was joined in the attack by more advanced models. The Doctor, Nardole and the Bill-Cyberman were able to halt the attack, though it cost the Doctor his life. The Mondasian Cybermen could kill with an electrical discharge, and their head-mounted lamps now also contained an energy weapon - and it was one of these which was used on the Doctor. Nardole remained behind with the colonists to help defend them against future attacks. Bill escaped her Cyber-existence when she was rescued by the alien pilot who had taken on the form of her friend Heather. Bill left her Cyberman shell to travel the cosmos in spirit with Heather.
Appearances: The Tenth Planet (1966), World Enough And Time / The Doctor Falls (2017).
- The new Mondasian Cybermen were supposed to have appeared briefly at the beginning of Twice Upon A Time, but the scene was deleted prior to broadcast. This Christmas Special does include flashbacks to the original 1966 adventure. Earthshock also features a brief glimpse of the Mondasian Cybermen.
- Peter Capaldi claimed from the outset that he would like his Doctor to meet the original Cybermen, so it was only right that he got to do so in his last season finale.