Public priests were appointed by the collegia. Once elected, a priest held permanent religious authority from the eternal divine, which offered him lifetime influence, privilege and immunity. Therefore, civil and religious law limited the number and kind of religious offices allowed an individual and his family. Religious law was collegial and traditional; it informed political decisions, could overturn them, and was difficult to exploit for personal gain. Priesthood was a costly honour: in traditional Roman practice, a priest drew no stipend. Cult donations were the property of the deity, whose priest must provide cult regardless of shortfalls in public funding – this could mean subsidy of acolytes and all other cult maintenance from personal funds. For those who had reached their goal in the Cursus honorum, permanent priesthood was best sought or granted after a lifetime's service in military or political life, or preferably both: it was a particularly honourable and active form of retirement which fulfilled an essential public duty. For a freedman or slave, promotion as one of the Compitalia seviri offered a high local profile, and opportunities in local politics; and therefore business. During the Imperial era, priesthood of the Imperial cult offered provincial elites full Roman citizenship and public prominence beyond their single year in religious office; in effect, it was the first step in a provincial cursus honorum. In Rome, the same Imperial cult role was performed by the Arval Brethren, once an obscure Republican priesthood dedicated to several deities, then co-opted by Augustus as part of his religious reforms. The Arvals offered prayer and sacrifice to Roman state gods at various temples for the continued welfare of the Imperial family on their birthdays, accession anniversaries and to mark extraordinary events such as the quashing of conspiracy or revolt. Every January 3 they consecrated the annual vows and rendered any sacrifice promised in the previous year, provided the gods had kept the Imperial family safe for the contracted time.

What group selected public priests in Rome?