A dastur holds the most senior rank of the Zoroastrian priesthood, historically presiding over a fire temple district or a major fire temple itself, particularly an Atash Behram, the highest of the three grades of consecrated fire in Zoroastrian practice, whose establishment and ongoing ritual maintenance require the participation of numerous priests over an extended, elaborate consecration process. Zoroastrian fire temples are graded according to the complexity of the fire's original consecration and the resulting purity and sanctity attributed to it, the Atash Behram standing above the Atash Adaran and Atash Dadgah, and a dastur's authority and prestige is closely tied to association with the more senior grades of temple and fire.
The office and the wider Zoroastrian priesthood are today divided between the two main branches of the faith, the Parsi community centered in India, chiefly Mumbai and Gujarat, descended from Zoroastrians who emigrated from Persia beginning around the tenth century CE, and the smaller Irani Zoroastrian community that remained in and later re-emigrated from Iran, each maintaining its own priestly lineages and, in some liturgical and calendrical details, distinct practices, reflecting centuries of separate historical development between the two branches.