Mondas Mondas was the twin planet of Earth and original homeworld of the Cybermen . In ancient times , it was dislodged from its old position out into space when the Moon was formed . The Cybermen eventually learned to pilot their planet and took Mondas back to Earth , where it was destroyed . Native life . Originally , the Mondasian s resembled the human s of Earth in every respect . ( TV : " The Tenth Planet " , AUDIO : " Spare Parts " ) Some accounts show that in the same way that parallels to humans existed on Mondas , Lizard King s and Sea Devils shared the planet with dinosaur s , Cybermen , ( COMIC : " The Dead Heart " ) and ape s . ( COMIC : " The Prodigal Returns " ) Golgoth , a bipedal reptilian god in physical form , also lived on Mondas at this time . ( COMIC : " The Cybermen " ) The Museum of the Last Ones had specimens of extinct species from Mondas . ( PROSE : " The Last Dodo " ) Geography . Mondas was identical to Earth , even down to the size and shapes of its continent s . The one major way that it differed to Earth was that its continents were upside down in relation to Earth . However , it had no visible clouds in its atmosphere at that time . ( TV : " The Tenth Planet " ) History . Creation . According to one account , Mondas originated as Marinus , a planet previously visited by the First Doctor , the Cybermen having " quick - evolve d " from the Voord . This account claimed that Marinus was known as Planet 14 . ( COMIC : " The World Shapers " ) This was contradicted by the Twelfth Doctor , who knew that while Cybermen did evolve on Marinus , they originated separately from the Mondasian Cybermen , through parallel evolution . ( TV : " The Doctor Falls " ) According to another account , Mondas was created by the Constructors of Destiny as an experiment of sorts to see how it would differ from Earth . ( PROSE : " The Quantum Archangel " ) Originally , Earth and Mondas occupied the same orbit in the solar system . It was stated that " Mondas " was another name for Earth in one of the ancient languages . ( TV : " The Tenth Planet " ) Under Lizard King rule . Mondas had , like Earth , at one time , an intelligent reptile species . ( COMIC : " The Cybermen " ) A cosmic cloud once appeared near Mondas . A Cyberman from the future came through the cloud and was captured by the Lizard Kings . At this point , the Lizard Kings had never encountered Cybermen before . They were intruiged by the cloud the Cyberman came from and sent a modified ape - servant through the cloud to investigate if it was a viable way to escape the rogue planet which was approaching Mondas fast . The Lizard Kings never left Mondas , ( COMIC : " The Prodigal Returns " ) and the sudden arrival of a moon between Earth and Mondas caused an upset in the gravitational equilibrium of Mondas , causing it to escape its orbit ( AUDIO : " Spare Parts " ) and begin drifting on a journey to " the edge of space " . ( TV : " The Tenth Planet " ) While parts of Mondas still had a tropical climate , the Lizard Kings encountered the Cybermen of their own time and warred with them . ( COMIC : " The Dead Heart " ) Golgoth appeared and destroyed all but one Cyberman and finally destroyed the lone survivor . ( COMIC : " The Cybermen " ) By the time that Mondas was well and truly separated from Earth , the Lizard Kings had fallen and the Cybermen became the new rulers of Mondas . ( COMIC : " The Prodigal Returns " ) Evolution of the Cybermen . A cosmic cloud appeared near Mondas , providing a temporal link to its past . After an ape modified by the Lizard Kings came through the cloud and was captured by Cybermen , they became curious about the cloud and decided to send a scout through it see if there were more apes that could be converted into Cybermen on the other side . ( COMIC : " The Prodigal Returns " ) Some centuries after , Cybermen had been wiped out and human - appearing Mondasians of roughly 20th century technological development had replaced them . Archaeologist s discovered remnants of the Cybermen . ( COMIC : " The Ugly Underneath " ) Further away from the life - giving warmth of Sol , conditions on the planet grew steadily worse . This forced the inhabitants to relocate underground in order to survive . They had by this time developed a society parallel to that of 1950s England . The Cybermen took over and enforced cyber - conversion for the surviving Mondasians . ( AUDIO : " Spare Parts " ) One Cybermen faction , the Mondan s , decided to stay on their homeworld . Another group , the Faction , more committed to total cybernetic conversion , pushed outwards in the solar system and colonised Planet 14 . ( PROSE : " Iceberg " ) The Mondans developed a drive which used electro - magnetic energy to push the whole planet through space . ( PROSE : " Iceberg " ) Return of Mondas . Their only recourse now was to use Mondas ' last remaining energy to return to the Earth ' s orbit and plunder her energy . ( TV : " The Tenth Planet " ) In 1873 , Mondas was located 200 light - year s from Earth . ( AUDIO : " The Silver Turk " ) In 1903 , after receiving a wealth of information from the future , Grigori Rasputin foresaw the return of Mondas . ( AUDIO : " The Wanderer " ) In 1984 , the Sixth Doctor left a damaged Cyber - Leader from the far future on Mondas knowing that it would be destroyed with the rest of the planet two years later . ( AUDIO : " The Reaping " ) In December 1986 , the Cybermen invaded the Snowcap tracking base in Antarctica while Mondas drew closer , draining Earth ' s energy to replace and supplement its own . However , the energy absorbed was too much , and Mondas disintegrated . The destruction of Mondas destroyed all of the Cybermen on Mondas and also killed all of the Cybermen on Earth , who were dependent upon Mondas for energy . As the planet plundered Earth ' s energy , the First Doctor ' s life - force was caught up in the maelstrom , triggering his regeneration into his second incarnation . ( TV : " The Tenth Planet " ) The Sixth Doctor would note Mondas ' s destruction as being part of the Web of Time as he thwarted an attempt made by future Cybermen in the previous year to save Mondas . ( TV : " Attack of the Cybermen " ) The official statement on Earth attempted to cover up the Cyberman invasion by claiming Mondas was an asteroid , known as " the Mondas Asteroid " , which went supernova before colliding with Earth . During Earth ' s war with the Myloki between 2066 and 2068 , Alex Storm found UN documents which revealed that Mondas was actually a planet . However , these documents were destroyed by " some ignorant clerk " to " save space " . ( PROSE : " The Indestructible Man " ) References . Facing the Cybermen on a Mondasian colony ship , the Twelfth Doctor recalled Mondas as the first of the worlds where they rose . ( TV : " The Doctor Falls " ) previously discovered the ship itself originated from Mondas . ( TV : " World Enough and Time " ) Behind the scenes . Origins of the concept . The idea of a parallel Earth opposite in orbit to Earth itself has occurred in pre - modern astronomy ( ) and some works of science fiction , though modern astronomers consider this unfeasible due to the orbital mechanics involved . The idea had earlier almost appeared in " Doctor Who " in the proposed Malcolm Hulke story " The Hidden Planet " . Apart from this , the idea occurs in countless comics , movies , novels and short stories . Continuity conflicts and ambiguities . The Cybermen origin story in " The World Shapers " portrays Marinus , Mondas , and the mysterious Planet 14 referenced in " The Invasion " as the same place . " Iceberg " and " " by David Banks , who had also played the Cyber - Leader on " Doctor Who " , explain it differently . According to the later , non - narrative reference guide , which this wiki , the drive that propelled Mondas through space was developed during the journey to " the edge of space " in order to effect a controlled return to their original orbit .