Smoking Mirror of Grism
"By the Smoking Mirror of Grism!" is an invocation or expostulation spat out by Alberto Malich when he returns to Unseen University during the events of Mort to find it staffed by wizards who aren't up to his crusty ideal of what they should be.
Grism is actually a real person in the real world that had the good fortune to interview TP back in 1986 for the Prestel based online magazine Earthlight Science Fiction & Fantasy.
Terry was taking part in a Micronet "Celebrity Chatline", where Prestel and Micronet users could email their questions in via the infamous Chatline system, and then read the answers as they appeared. A regular user and Micronet contributor known as GRiSm (a short name for Gary Richard Smith as needed for the turn-based space strategy game Starnet) asked if he could interview Terry directly for his magazine, and jokingly suggested that Terry used his nickname in the next book. Terry surprisingly agreed, but Grism dismissed it, not expecting it to happen.
Later, when reading the new book Mort, Grism was shocked to discover his name being dropped into the text. Terry originally referred to the character Grism as being some tentacled monster, but it's never been confirmed exactly what "The Smoking Mirror Of Grism" actually is.
At the 1987 World Science Fiction Convention in Brighton, Grism bumped into Terry and thanked him for his generous inclusion.
Apparently, a Grism is now some kind of Prism used in Astronomy, and also the name of an open source financial software package.
Annotation
"Smoke and Mirrors" is a Roundworld expression that alludes to the performances of stage conjurers who use actual smoke and mirrors to deceive the audience. The figurative use that is now more common refers to the obscuring or embellishing of the truth that is employed by spin doctors and the like in order to deceive the general public. This later usage comes from the writings of the American journalist Jimmy Breslin. In his Notes from Impeachment Summer, 1975, Breslin twice refers to smoke and mirrors being used in the US political scene:
"All political power is primarily an illusion... Mirrors and blue smoke, beautiful blue smoke rolling over the surface of highly polished mirrors... If somebody tells you how to look, there can be seen in the smoke great, magnificent shapes, castles and kingdoms, and maybe they can be yours."
"The ability to create the illusion of power, to use mirrors and blue smoke, is one found in unusual people."
Alternative Annotation
Tezcatlipoca was a central deity in the Aztec religion, associated with a wide range of concepts including; the night sky, the night winds, hurricanes, the north, the earth, obsidian, enmity, discord, rulership, divination, temptation, sorcery, beauty, war and strife. His name in the Nahuatl language is often translated as "Smoking Mirror" and alludes to his connection to obsidian, the material from which mirrors were made in Mesoamerica and which was used for shamanic rituals.