Over the long history of Indian religion Varuna's standing changed markedly. In the oldest layer he is among the highest gods, often paired with Mitra as the twin sovereigns who watch over oaths and order; but as the tradition developed, his cosmic sovereignty faded, and he settled into the more specialised role of the god of the waters, of the ocean, the rivers and the rain.
In classical Hinduism he is chiefly the lokapala or guardian of the western direction, lord of the seas, riding the sea-monster makara and carrying his noose, a dignified but no longer supreme deity. This decline of a once-great sky-god into a departmental god of water is one of the clearest examples in the record of how the relative importance of deities shifts over time.
Scholars have also long compared Varuna, as guardian of a cosmic-moral order and binder of the guilty, with sovereign and order-keeping gods in the wider Indo-European world, making him a figure of particular interest for the comparative study of religion. In his oldest form Varuna preserves something that later Hinduism developed in other terms: the sense of a moral order woven into the structure of the cosmos itself.