What is "mitra-varuna"

Mitra and Varuna are two deities ( devas) frequently referred to in the ancient Indian scripture of the Rigveda. They are both considered Ādityas, or deities connected with the Sun; and they are protectors of the righteous order of rta. Their connection is so close that they are frequently linked in the dvandva compound Mitra–Varuna.

For further information, see the articles on the separate deities Mitra (Vedic) and Varuna.