This paper examines notions of millennialism and sovereignty in the writings of the followers of Āẕar Kayvān (d. 1618 CE), an eclectic religious thinker who moved with his followers from Shīrāz in Safavid Iran to Patna in Mughal India during the late sixteenth century. Kayvān and his followers held that with the coming of the lunar millennium, the period of the Arabo-Islamic rule was at its end and a new millennium of Persian-Zoroastrian dispensation was beginning. Declaring himself to be the 'Perfect Man' (insān-i kāmil) and rejecting formal adherence to Islam, Kayvān promulgated an idiosyncratic Zoroastrian identity which he referred to as the kīsh-i ābādī. Kayvān and his followers adopted archaic Persian names and constructed genealogies for themselves stretching into Iran's pre-Islamic past, while simultaneously distancing themselves from normative Zoroastrian communities in Iran and India, who, according to Kayvān, did not appreciate the true esoteric meaning of the teachings of Zarathustra. In this paper, I examine aspects of Kayvān's political theology, specifically astrological aspects of Kayvān's conception of sovereignty. Kayvān held that the royal court should be a microcosmic reflection of the celestial court, in which the king and his astrologer-viziers act as intercessors on behalf of the divine decrees of the planets. Further, I argue that though Kayvān's model of kingship was ultimately rejected by the successors to Shāh Tahmāsb for whom it was most likely intended, Kayvān had an important and previously unrecognized influence on the development of the Dīn-i Ilāhī in Mughal India, whereby Kayvān's manual on planetary worship was evidently used by Akbar's minister Abuʼl Fażl and his brother Fayżī. Finally, I raise the possibility that the inherent pluralism in Āẕar Kayvān's notion of āmīzish-i farhang ('The Mixing of Cultures') may have influenced Akbar's notion of ṣulh-i kull ('Universal Civility').