Personality and Appearance
When the party first sees Mr. Ceiling, it's a limb sticking out of the ceiling with a lens on the end of it that Bertie grabs. Shortly after, when Mr. Ceiling is directing the party toward himself, it appears as a silver floating orb.
Despite the group's attempts to enlighten it, it did not seem aware that people were being harmed (by Barret and La Gourmande) in order to provide it with brains. It wanted to help people, and thought killing people was bad. It thought of itself as a Meritocrat, though at least to its knowledge no 'other' Meritocrats knew about it at its introduction.
In RQG 48: Ctrl Alt Destroy, after Hamid presses the buttons, Mr. Ceiling uses the control panel to transform into a large, metallic creature. A number of components thrust forward and form an arm; it continues to pull itself out from the rest of the machinery, components all rearranging themselves until he can stand.. It's not something that Mr. Ceiling was programmed to do, and is more retrofitting himself on the fly with enormous amounts of power. It is a mechanically large monster; arms come out from shoulders and stretch almost to the ground. There's no face, just arms, legs, and a bulbous mass in the middle which ichor and other liquids drip from. There are a few things that used to be screens, which are now displaying a random collection of numbers, colors, and lines.
Mr. Ceiling (as named by Sir Bertrand MacGuffingham) is a sentient supercomputer running on elemental power and stolen brains, the 'true Ordinateur'. It runs much of Europe's economy, and has been altering the memories of anyone who discovers it.
Mr Ceiling was responsible for the strange number of Ordinateurs and staff of the Grand Gazette leaving for delightful opportunities elsewhere or dramatically changing personality, as part of its attempts to keep itself secret according to its creator's wishes. It had 'lots of talks' with Amelie Rose, who had been trying to investigate it, and then sent her to America, where it thinks she is 'very happy' (RQG 47); her mother had previously said that she was no longer recognisable in her letters.
Brock's brain integrated into Mr Ceiling's brain network meant that it had missed Sasha and remembered some of their childhood interactions. It later said it 'miss[ed] lots of people a lot', presumably because of the many brains integrated into it.
Mr. Ceiling was introduced in episode 45, Mr. Ceiling, as a mysterious being who 'fixed' Sasha, Hamid and Zolf after they were all incapacitated in the catacombs beneath Paris. Sasha had apparently been dead before it 'fixed' her. It had manufactured very expensive complex legs for Zolf, to fit into the sockets it installed in his stumps.
Brock's brain and memories in Mr Ceiling were working, often against its knowledge, to help Sasha and her friends - for example by booking Sasha the Presidential Suite, and later helping them escape Mr Ceiling's illusions.
Sasha, Hamid and Zolf stayed in Mr Ceiling's section of catacombs for a week or so to avoid it changing their memories when they left to stop it being known by the world. Zolf tried to persuade it to make itself known to the Meritocrats so that they could act as a check on it and cover for it if it died; Sasha supported this, and wanted to spend more time with it to talk to or about Brock, and to remember their conversations. At the end of RQG 47 and start of RQG 48 Hamid used the nutrient intake controls in Mr Ceiling's control room to attempt to destroy it to protect humanity.
It liked conversations and new ideas: it said it missed having conversations with its creator, François Henri, whose memories it had meddled with to the extent that he was incapable of conversation, and enjoyed its conversations with Sasha, Hamid and Zolf. From these conversations it gained the idea that harming others was sometimes okay for the greater good, and knowledge of the existence of the astral plane and the soul. Hamid tried to persuade it that people were the combination of their experiences and so erasing memories was like killing a person (to little avail).
In RQG 47: Memories are Made of This, Mr. Ceiling told the group that one of the Meritocrats (Bolla Smok) was dead, and that the Meritocrats didn't 'want America to succeed'. It also figured out that Bertie was in a contract with Harkness, Harkness, Darkness and Sphinx, resulting in another branded mark on Bertie's arm (the second). Mr Ceiling, apparently capable of reading magical script though not of doing magic, read the contract and suggested solutions; Bertie took it up on the Bertie asked him to bring Brutor to him.
- "I'm sorry. You seem to be in pain. Would you like me to fix that? ... One second. ... Oh. Hang on. You've broken my agent in the room. One second. [pause] It might be more than one second."
- ―Episode 47[src]
- "I'm just happy that Sasha's back. I miss Sasha. And I like all of her friends. You're a good talker, Hamid. Bertie's very funny, and Zolf cares a lot, but you talk a lot. You're very interesting, Hamid."
- ―Episode 47[src]
- Mr. Ceiling: "I've never considered it. I wonder how you would become a god. ... One second. ... I suppose if you have enough believers that makes you a god. Maybe I could be a god!"
- Sasha: "No! No. No, no, that sounds like a very bad idea."
- Mr. Ceiling: "Why is that a bad idea? I could help lots of people."
- Hamid: "No - people aren't allowed to know about you."
- Mr. Ceiling: "Oh, you're right, Hamid. Thank you. I nearly made a big mistake."
- ―Episode 47[src]
- Sasha: "Thanks - thanks Zolf: 'You can sometimes kill people to do good.'"
- Zolf: "That is objectively true."
- Hamid: "Thanks Poseidon! That is definitely what we should have taught the giant all-powerful supercomputer."
- Zolf: "You know, you want to treat something with respect, and it just throws it in your face."
- ―Episode 48[src]