Irstats were Tarasin tribal groups that dwelled on the planet Cularin. Irstats usually consisted of between about thirty or fifty members, although some irstats were larger and the Hiironi irstat—the most populous irstat—had over three hundred members. Each irstat was led by an Irstat-Kes, who was usually the second oldest female member of the tribe. The eldest female in the irstat held the title "Mother" and acted as a figurehead for the tribe, by embodying the best aspects of Tarasin culture. Mothers and Irstat-Kes' were often Force Adepts, although this was not mandatory.