Aza is the Tuvan name for a malignant, devil-like spirit bound up with disease, death and haunted ground. In myth it manifests as the evil spirit of a particular sickness or place, assuming forms such as a shaggy old woman with great teeth or a bony man with a long tail. Yet the aza is double-edged: in shamanic incantation the same name denotes the lower-world spirit-helper of a shaman whose initiation came from below, so that the practitioner draws strength from the very power that afflicts. The word belongs to a broad Turkic demonological vocabulary attested across Southern Siberia, and in Tuvan tradition the aza is counted, with the albys, among the dark agencies that both plague human beings and animate the darker forms of shamanizing.