Kalki is the tenth and final avatar of Vishnu, the one who is still to come. Where the earlier avatars appeared in ages past, Kalki belongs to the future: he is to arrive at the end of the present age, the Kali Yuga, the last and most degenerate of the four world-ages, when righteousness has almost vanished from the earth, rulers have become predators, and the moral order has collapsed. He is described as riding a white horse and wielding a blazing sword, appearing to destroy the wicked, to bring the corrupt age to its close, and to inaugurate a new Satya Yuga, an age of truth, so that the cycle of the ages may begin again.
The Puranas place his birth in a village called Shambhala and give the names of his family, casting the cosmic renewal in the concrete terms of a human advent. Kalki expresses a distinctive feature of Hindu time: history is not a single line running to one end, but a vast wheel of ages that decline and are renewed without cease, and Kalki is the hinge of that renewal, the destroyer of a spent world who is at the same time the herald of its rebirth. The figure of a future saviour riding to end a fallen age has invited comparison with messianic expectations in other traditions, though Kalki is set firmly within the cyclical framework of the yugas.