Long before Lord Indra became the leader of the Devas, the most important personage in the holy world was considered to be Lord Varuna, the god of all forms of water including oceans and water present in the underworld, as well as the God of universal law and celestial order, known as Rta. As you can see, Lord Varuna held a very important role indeed to ensure all the parts of the earth and the universe co-existed in harmony, and thus, was considered the most important god until he was replaced in importance by Lord Indra, and then later, the Trinity of Lords Brahma, Vishnu, and Shiv.
It is said that praying to Lord Varuna is extremely good for people, who wish to improve the quality of their lives, for married or other long-term couples, who are facing relationship discords and restore peace in your body, mind, and home. The mantra that is used to worship rain god is as follows:
“Aum Jalbimbaye Vvidmahe
Nila Purushaye Dhimahi
Tanno Varunah Prachodayat”
In this chant, people pray to Lord Varuna to still the waters of their mind and grant them higher intellect and inner peace. One of the most popular divine stories involving rain god is when Lord Ram had to cross a river and reach Lanka to rescue Mata Sita, who was kidnapped by Ravana. It is said that for three whole nights and days, he prayed to rain god and asked him for guidance as to how he and his troops to cross the waters and reach their destination, but he received no response from the water god. In his rage, he blindly started shooting arrows in the water to cause damage to it and the living things in it. When he was about to use the most powerful divine weapon of all, the “brahmastra,” Rain god appeared before him and requested him to keep it aside and use it in the war against Ravana. He mentioned as he didn’t himself know of a way to help him he had not appeared earlier, but he could help by calming the waters so that the army could try and find a way to cross over. Rama’s faithful army built a bridge of large stones, and thus, rain god played a role in the epic Ramayana battle.
Lord Varuna is, in fact, worshipped in many countries and religions. He is also mentioned in Buddhism, is worshipped by Zoroastrians, and by people living in Japan. There is a temple dedicated to rain god in many parts of India and in Shinto, Japan too.
Another story that involved Lord Varuna is that of him and Sage or Rishi Vashishta. The Rajguru of the Devas and Lord Varuna had shared a very long lasting and deep friendship, which was jeopardized because of a mistake that the sage had committed. As the Lord of Law, Varuna punished Vashishta but later pardoned him after the latter recited the Varuna Gayatri and appealed to his sense of fairness and justice.