Short answers, pulled from the story.
Varuna stands as a central figure among the earliest Hindu deities and functions as a universal monarch who rules the sky. He embodies divine authority over all creation while maintaining truth and rta which represents the cosmic and moral order governing both nature and human conduct.
The transition from Vedic supremacy to water lordship occurred gradually across centuries of religious development by the time of the Itihasa-Purana period. This shift reflects broader theological changes within Hindu tradition over millennia where waters evolved from metaphysical concepts into literal physical bodies under his direct command.
Scholars trace the name Varuna back to the verbal root vri meaning to surround cover or restrain bind combined with suffix al una. Sanskrit verb vri translates to rain pour indicating moisture rather than binding as primary meaning according to modern scholarship rejecting earlier Indo-European derivations.
Despite his frequent mention he is the sole focus of only ten specific hymns within this ancient scripture. These include 1.25, 2.27 through 30, 7.86 to 88, 8.8, and 9.73 among numerous other appearances.
The Mahabharata describes his residence beneath the waters in Nagaloka an oceanic realm filled with pure white palaces. There he sits enthroned beside his queen surrounded by aquatic beings including naga serpents daityas sadhyas and various river goddesses.