Mentioned in The Colour of Magic, Pitchiu was the ruler of an unknown nation on the Disc. He commissioned Goldeneyes Silverhand Dactylos to build him an army of Metal Warriors to guard his tomb. Pitchiu was the first of several employers to richly reward Dactylos and then critically injure him to prevent the craftsman from making any more great works for other customers. In Pitchiu's case, the reward took the form of gold, followed by Dactylos having his eyes put out. However, Dactylos learned "to hear the temper of metals and to see with his fingers", and made two golden eyes.
As for the Tomb of Pitchiu and Pitchiu's mechanical army, nothing further has ever been mentioned about them.