He first appeared in the novel Small Gods as a minor character. He was one of the History Monks, a member of a Buddhism-like sect, that maintained Discworld history, based on the huge History Books in their Ramtop monastery. He spent much of the novel in the background, disguised as a simple sweeper. He also deliberately changed the course of history because he didn't like the way things "should" go, replacing a horrific war with a century of peace.
Lu-Tze had a more substantial role in Thief of Time, in which we learn that he is not a monk at all, but "merely" a sweeper at the Monastery of Oi-Dong. In fact, he uses the same trick (that no one notices a sweeper) in the monastery as he does when out in the world, and has learnt as much about the nature of time as some of the higher monks simply by tidying up the classrooms. Everyone knows Lu-Tze's name, as one of the best monks on the field, but few realise who he actually is.
Lu-Tze has a deep respect for the Abbot of Oi-Dong, but apart from him generally distrusts authority. He has a highly irreverent attitude that angers the senior monks all the more because he's so good at what he does. Not being holy gives him certain freedoms not generally available to the monastery's agents, one of which is saying what he thinks. He has seen many changes in the monastery, and disapproves of most of them. He is particularly concerned with an apparently recent focus on martial arts, believing that this sort of thing is unlikely to solve anything.
He is, however, very good at martial arts when he needs to be, and is the only known master of "Déjà fu", in which the hands move in time as well as space. Generally he relies on the fact no-one notices a sweeper, a well-honed ability to talk his way out of anything and "Rule One". Rule One is "Do not act incautiously when confronting a little bald wrinkly smiling man". (Due to the Disc's narrative causality such a person is almost always a highly-trained martial artist. Rule Nineteen is: "Remember Never to Forget Rule One. And always ask yourself: How come it was created in the first place?") It is the opinion of many that Lu-Tze uses Rule One to bluff his way out of trouble, but, if necessary, he can prove it's no bluff. He does this towards the end of Thief of Time by defeating Lobsang Ludd (then incarnated as the personification of Time) in a fair fight, in front of a crowd of higher monks. As he said, "Def'nitely give the ol' Rule One a fillip."
Lu-Tze is a follower of the Way of Mrs. Cosmopolite, Mrs. Cosmopolite being a dressmaker in Ankh-Morpork. This involves such supposed "koans" as "It never rains but it pours", "Do unto otters as you would have them do unto you" (He has shown doubts about the accuracy of his recording on this one) "Because", "Eat it up, it'll make your hair curly", and "Well, I'll go to the foot of our stairs". It is not clear how much he takes this seriously, and how much it's just a way of winding up the monks. Probably inspired by Lu-Tze's success however, a fair amount of young saffron-clad men from the area around Oi-Dong have taken up the Way (Wisdom is one of few things that seem greater when far-off), regularly spying on Mrs. Cosmopilite, which she disapproves of most strongly. Their efforts have even spawned a martial art of its own, in which the practitioners shout incomprehensibly at each other before bashing their opponent over the head with a broom.
When not seeing to the duties of a sweeper, Lu Tze works in his Garden of Five Surprises (the little bridge that tilts, throwing you into the carp pool, the way the little daisies spray you with venomous pollen, the bronze butterfly that flaps its wings when you breathe on it, the yodelling stick insect and a cheap carnival mask), works on the monastery's Clock Path or cultivates his bonsai mountains. It is unknown just how these mountains work, but what has been revealed indicates it is based on very thorough checking of the prospective rocks (you have to find what would in normal events become the top of the mountain) and devices which influence the morphic field of the forming mountain to make it much smaller.
Lu-Tze is the only known practitioner of Déjà fu; best described as "the feeling that you have been kicked in the head this way before."
In Déjà fu, the practitioner travels in time as well as space. He can go back in time and hit his opponent with a series of punches. From the opponent's point of view, the practitioner is standing motionless in front of him, but he feels the effects from the past attacks. Also, the practitioner can put parts of his opponent's body out of time with respect to the rest of the opponent, making attacks ineffective, preventing the opponent from moving or causing the opponent to trip.
Other forms of martial arts on the Disc (and Lu-Tze's opinions on them) include:
- Okidoki ('Just a bunch of bunny hops')
- Shiitake ('If I wanted to thrust my hand into hot sand, I'd go to the seaside')
- Upsidazi ('A waste of good bricks')
- Tung-pi ('Bad-tempered flower arranging').
- No Kando ('You made that one up').
It is not immediately clear who on the Discworld practices these arts, though they are mentioned in reference to the monks of time, who are known to practice martial arts in general.
The term "Déjà fu" is a punnish portmanteau of "Déjà vu" (a feeling that you have experienced something before even though you haven't) and kung fu (a term used in the West to describe the Chinese martial arts).