Short answers, pulled from the story.
Varuna is one of the earliest deities in the Hindu pantheon, initially revered as the god-sovereign of the sky and enforcer of ṛta, the cosmic and moral order. Over time, his role shifted from omnipotent sky-god and ethical judge to lord of all waters, ruling oceans, rivers, streams, and lakes. He is depicted riding the mythical sea creature Makara and holding a noose called the pasha.
In the Rigveda, composed roughly between 1900 and 1200 BCE, Varuna is among the most prominent deities, appearing in numerous hymns including 1.25, 2.27-30, and 7.86-88. He is portrayed as a divine king of the sky, the upholder of ṛta, a deity associated with water, and a wielder of maya, cosmic creative power. He is called Sindhu-pati, lord of the ocean, and is described as observing all human actions through celestial spies.
In the early Vedic period Varuna was supreme sky-god and moral sovereign of the cosmos; by the time of the Itihasa-Puranas he had become lord of all waters, residing in an underwater palace in Nagaloka. In the epics and Puranas, composed between roughly 400 BCE and 1000 CE, he is reduced to a dikpala, guardian of the western direction, and is subordinate to deities such as Vishnu, Krishna, and Shiva.
Comparative mythologists, including Georges Dumézil in his 1934 study Ouranos-Varuna, have identified parallels between the two deities, suggesting a common Proto-Indo-European origin. Both names are thought to derive from a root meaning to bind or to cover, and both gods are associated with sovereignty, cosmic law, and restraint. The direct linguistic derivation of the Greek name from this root is now widely rejected, though the structural mythological similarities remain recognized.
In the Ramayana’s Yuddha Kanda, Rama performs a three-day penance to Varuna seeking passage across the ocean to Lanka, but Varuna remains silent until Rama threatens to unleash the Brahmastra weapon. Varuna then appears and, rather than parting the sea, instructs Rama to build a bridge, known as Rama Setu, through the vanara architect Nala. In the Uttara Kanda, Varuna takes the form of a swan to hide from Ravana’s conquests.
In Japanese Buddhism, Varuna is called Suiten, meaning water deva, and is one of the Twelve Devas known as Junitten. One Shinto shrine dedicated to him is the Suitengu in Tokyo. In Sindhi Hindu tradition, Jhulelal is believed to be an incarnation of Varuna, celebrated during the Cheti Chand festival marking the mythical birth of Uderolal in the year 1007. Theravada Buddhism’s Pali Canon recognizes Varuna as a king of the devas who takes the third seat in the divine assembly.