Mustrum Ridcully, D.Thau., D.M., D.S., D.Mn., D.G., D.D., D.C.L., D.M. Phil., D.M.S., D.C.M., D.W., B.El.L., is a wizard in the Discworld novels of Terry Pratchett. He was introduced in Moving Pictures as the latest Archchancellor of the Unseen University.
At the time he became Archchancellor, he had not been seen at the University for forty years, having become a Seventh Level Wizard (there are, naturally, eight levels of wizardry on the Discworld) at the exceptionally young age of twenty-seven, before leaving the university to look after his family's land. The wizards, knowing he liked the countryside, assumed he would be a "roams the forests with every beast his brother" type, very similar to Radagast, and easy to deal with. As it turned out, Ridcully did like the countryside, but mainly as a place to kill things. He owns several hunting crossbows and is much given to using the corridors of Unseen University as a shooting range. In Lords and Ladies, it is revealed that he does a lot for rare species, keeping them rare for a start. He loves sport and healthy living, and was a Rowing Brown for the University in his youth. Since wizards' favourite sports traditionally are things like Competitive Eating and Extreme Napping other wizards find him very tiring to be around for any length of time.
He is not stupid, and in fact has a mind like a freight train, but finds it very difficult to deal with unexpected information, and generally ignores it until it goes away or becomes someone else's problem. He holds the view that if someone is still trying to explain something to him after about 2 minutes, it must be worth listening to, and if they give up earlier, it was not worth bothering him with in the first place. Usually, the person doing the explaining is Ponder Stibbons. He is also both literal and practical almost to the point of insanity, and though this usually works out in the end it makes life hard for those around him.
Ridcully is generally portrayed as being stubborn, and he only rarely listens to someone else. However, he has shown the occasional flash of magical skill. For example, in Moving Pictures, the Bursar is surprised to discover Ridcully's adeptness at using a magic mirror (which, like most Discworld scrying devices, is hard to steer) to find something (as Ridcully put it, he didn't have time to be crawling around the woods hoping something he could shoot would come by). It's also implied that he has some degree of practical magic knowledge--instead of using a 'thaumometer' (a device that gives a numerical measurement of a magic field's strength), he licks a finger and notes the colour and size of the small spark it gives off in the air (The Last Continent). He also tends to be more practical than most of his fellow wizards such as when he revives Mr. Teatime ("Teh-ah-tim-eh, everyone gets it wrong") by hitting him on the chest before any of his fellow wizards could whip up a spell.
He tends to move with little or no thought of the future or the consequences that might be involved, as in Hogfather where upon discovering a door, (hidden behind a bookcase, boarded up, with a sign saying 'Do not open under any circumstances') promptly has it opened, where he finds a bathroom designed by Bloody Stupid Johnson. Upon his first attempt at showering and trying a curious knob labelled 'Old Faithful', which causes the shower to send a jet of water out that rivals its namesake, his screams convince Modo to turn off the water. Undeterred by this, he returns to the shower only to try the 'Musical Pipes' enhancement, interlocked with the university's organ upon which the Librarian was playing Bubbla's Catastrophe suite. Following this second, seemingly disastrous, incident, Ridcully had Modo permanently seal the bathroom up again.
He has stabilised the structure of Unseen University (which used to be based on killing wizards more powerful than you) by being impossible to kill. It is interesting to note that not only is he the first Archchancellor to last more than one book, but the rest of the faculty have been given more development as well, suggesting an increased survival rate amongst all senior wizards. They do not seem to appreciate this, however, due to Ridcully's exhausting personality. In particular, the Bursar has become a nervous wreck since Ridcully's arrival.
He has a curious understanding of sanitation, and frequently refers to things as 'unhygienic'. There is a reference concerning this in which he mentions his father suggesting the existence of a Verruca Gnome, who would afflict whoever went around barefoot.
Oddly, the faculty member he gets on best with seems to be Ponder Stibbons. He never understands what Ponder is saying, and Ponder never expects him to, but at least the young man is doing something, which is more than can be said for the rest of them. He is also quite fond of the Librarian, dismissing a rather snide question about whether it's appropriate for UU's librarian to be an ape with the response, "... he's the only one of you buggers who's awake more'n an hour a day." He has an (understandably) low opinion of most other wizards, but will not tolerate disrespect of wizards or wizardry by other people, once promoting a wizard (Devious Collarbone) from graduate student to Professor just because some "civilians" were being rude to him. He has a cordial but somewhat edgy relationship with the Patrician - while wizards believe that they answer to "higher laws" than governments, they usually comply with the city's requirements because it would be impolite not to.
His brother is Hughnon Ridcully, High Priest of Blind Io, and Ankh-Morpork's religious spokesman. While priests and wizards are traditionally at odds due to philosophical differences, neither Ridcully is of a particularly philosophical frame of mind, and they tend to ignore this. Despite Samuel Vimes's legendary dislike of magic, he also gets on well with Ridcully, as both of them share the belief that the most important thing about magic is knowing when not to use it as well as the fact that the sort of crimes wizards tend to commit typically fall outside Vimes' jurisdiction.
In Lords and Ladies we learn he had a relationship with a young Esme Weatherwax, some fifty years before becoming Archchancellor (indeed it is suggested in the book that, in one of the many parallel universes adjacent to the one on which the Discworld novels take place, alternate versions of Ridcully and Granny Weatherwax are married and have children).
Very strong, very powerful, and very hard to divert once it gets going. He is also an Autocondimentor and is skilled in making his very own version of the legendary Wow-Wow sauce.