Colony ship ( World Enough and Time ) A Mondasian colony ship was travelling from Mondas to pick up colonists . When the ship almost traversed into a black hole , the crew experienced the effects of time dilation , where time on the lowest decks of the ship was travelling faster than on the upper decks . Layout . The ship was approximately 400 mile s long and around 100 miles wide . Decks . The ship contained over a thousand decks , each of which presented a Mondas ian environment . These included : Each level from the bottom and up would move a little slower than the one below it , due to the time differential , from proximity to the black hole . ( TV : " World Enough and Time " , " The Doctor Falls " ) Crew . At take off , there were fifty crew members aboard the ship . They included Jorj : a member of janitor ial staff . Following the effects of time dilation , the ship became filled with generations of lifeforms , each descended from the ship ' s crew . Technology . The ship was fitted with super - fast inertia lift s and was propelled by rear thruster s . Aboard the lowest decks , evolution of technology was advanced . In order to adapt to expiring environments , an artificial evolution was devised . The Mondasian inhabitants were gradually upgraded into Cybermen . ( TV : " World Enough and Time " ) History . The colony ship was commissioned to transfer inhabitants of Mondas , for which it was headed with a skeleton crew of 50 , including the janitor Jorj . En route , it was drawn into the gravity well of a black hole . The crew sent a team of 20 to the lowermost level , floor 1056 , to reverse the engines and pull the ship free . However , time dilation caused by the black hole ' s gravity resulted in time passing much more slowly at the upper parts of the ship , which were closest to the black hole . Due to time dilation , the team at the bottom of the ship found that they experienced over 500 years for every day that passed on floor 0000 . Thus , after reversing the engines , they and many generations of their descendants lived out their lives on floor 1056 . They built an industrial civilisation , but eventually they began to run out of resources and their environment became irreversibly polluted . At one point , an expedition was sent to floor 0507 to explore the possibility of moving there , but again due to time dilation they were never heard back from again . At some point , , after being banished from Gallifrey , landed on floor 1056 . The Master ' s attempt to escape the black hole by going too fast burned out his TARDIS ' dematerialisation circuit and stranded the Master on the colony ship . The Master " killed a lot of people , took over the city , lived like a king " before the people of floor 1056 tired of his cruelty and overthrew him . The Master was forced into hiding as " Mr . Razor " , the caretaker of the hospital . Eventually , the people of floor 1056 were forced to convert themselves into cybernetic humanoids to survive . The prototypes would venture to the upper floors to take the rest of the crew members for conversion , leaving only Jorj as he wasn ' t completely human . Eventually , the Twelfth Doctor , , Bill Potts and Nardole picked up Jorj ' s distress signal . ( TV : " World Enough and Time " ) On Floor 0507 , there resided a group of farmers who possessed rifles . They were faced by the prototypes that had travelled to their floor from 1056 . They spent the night shooting them down , then stringing them up on wooden crosses during the day . They were plagued by these " cyber scarecrows " ( as one child called them ) for an unknown amount of time - they had left floor 1056 for several hundred from their perspective . One day , a shuttle raft blasted through the floor , containing the Doctor , a cyber converted Bill Potts , the Master , Missy and Nardole . With the Doctor injured , Nardole rallied the town over the coming weeks to prepare for a Cyberman invasion ; the prototypes were merely the advance guard . As such , the siege of floor 0507 began . Nardole hacked the floor to ignite certain fuel lines around the floor to fool the Cybermen their technology was a threat to the Cybermen . Floor 507 was ultimately destroyed by the Doctor along with most of the Cybermen . Nardole moved the townspeople to floor 502 where there was another solar farm and they would be safe for years until the surviving Cybermen could regroup and find them . During the siege of floor 507 , Missy provided the Master with a new dematerialistation circuit for his TARDIS , allowing him to depart the colony ship . However , before he left , Missy forced a regeneration upon the Master and the Master killed Missy with his laser screwdriver . The Doctor also stayed behind on floor 507 to delay the invading Cybermen while Nardole evacuated the townspeople , using the sonic screwdriver to detonate more fuel lines until he was eventually shot down by the Cybermen , beginning his own regeneration . Before the process could take hold , he used the sonic screwdriver to detonate the entire floor , destroying the majority of the Cybermen . ( TV : " The Doctor Falls " )