The mus are a race of diminutive rodents that resemble bipedal mice. They live in regions normally unvisited by larger humanoids such as forests, isolated valleys, and forgotten ruins, but they are also known to inhabit large cities, where their tiny empires grow powerful beyond the notice of the city's conventional inhabitants. Mus communities are ruled by hereditary sultans, and they create elaborate dwellings, decorated in the fashion of the most luxurious cities.

The mus also dress well, favoring lavish but tasteful garb from silken trousers, curly-toed slippers, turbans, embroidered vests, fezzes, and low-crowned tasseled chapeaux. Mus also love lavish jewelry - rings, necklaces, bracelets, and broaches of tiny size but superb workmanship. Though of good alignment, they tend to avoid contact with the outside world, preferring to keep their hidden empires a secret from others. Mus sorcerers command many defensive spells and can make encounters with the little creatures challenging even for experienced adventurers. If aided or shown friendship, the mousefolk may become companions or allies, but always ask that their friends keep their secrets.