Floor 0000

Floor 0000 was one of over a thousand decks on a Mondasian colony ship. The floor contained the flight bridge for the vessel.

When the colony ship almost traversed into a black hole, each of the ship's floors was affected by time dilation. Located at the top end of the ship, time travelled slower on floor 0000 than on any of the floors below. For example, 2 days and 10 hours at the top equated to just over 1000 years for those on floor 1056.

Colonisation
The ship was travelling from Mondas to pick up colonists. When the ship almost traversed into a black hole, around twenty crew members were sent to the bottom of the ship, approximately to the location of floor 1056, to reverse the rear thrusters. Unable to return to the top of the ship, the crew members remained at the bottom.

Arrival
The Twelfth Doctor, deciding to see how far 's reformation has progressed, answers a spaceship distress call. He sends Missy out of the TARDIS to deal with it, having Bill Potts and Nardole acting as her companions. Jorj, a janitor left alone at the top of the ship, appears. He panics at the presence of a human, shooting Bill through the chest.

Bandaged figures come out of the lifts and take Bill's body downstairs. They tell the others she will be "repaired", but not returned. After a short time, the Doctor, Missy and Nardole head down after her. However, due to the time dilation, years have passed for Bill. By the time they arrive on floor 1056, she has been converted into the first fully cybernetic humanoid. (TV: World Enough and Time)

Nardole stole a shuttlecraft and they all went up until crashing on floor 0507. They fought the pursuing Cybermen and evacuated the residents on that floor to a higher level. The Doctor and Bill stayed behind to hold off the Cybermen and destroy them all, though the Doctor is fatally injured.

Departure
However, Heather finds Bill through her tears and makes her into a being like herself. They bring the Doctor back to his TARDIS on floor 0000 and Heather, now able to pilot anything, takes off from the ship. (TV: The Doctor Falls)