Thaumaturgists

Even lower on the food chain of magic than Conjurors. Described as the background technical staff, the lab assistants, the ones who sweep up the ceremonial octogram after the ritual, and largely formed from the ranks of those who fail their exams for wizardhood but still want some sort of association with the world of magic.

If a spell calls for a root of mandrake that screams in the high ultrasonic when uprooted (with consequent sensations of what Magrat Garlick called "dire rear"), or for 10cc of fresh tiger semen, who do you think is sent out to garner such ingredients?

No wonder Rincewind wanted to cling on to Wizzardhood at all costs, if this was the only possible alternative for him, as a failed wizard...

In Equal Rites, they were likened to "lab technicians called Igor", but this since has been superseded by the advent of the real Igors.