Here it goes
Lord Varun was the first lord during the Vedic period. He was replaced by Lord Vishnu later ..
Varuna is vedic god, the first creator, the most ancient god of the Universe.
Where as Vishnu is falsity, a myth, a false hero from Vishnu Purana, created by Vaishnavites who wanted to digress away from Vrta and Vedas.
No one can exist on earth if not for Varun’s Water. Vishnu has stolen the identity of Varuna , in truth, he is just another local god.
Varun in Mahabharata & Ramayana
In Mahabharata, there is a reference to Lord Varuna. Here, we find him portrayed as the Lord of waters. It was when Krishna and Arjuna were in the Kandeva forest. They took the help of both Lord Agni and Lord Varuna. Lord Varuna gives Arjuna a bow called Gandia. It does not possess any weakness and is equal to a thousand bows.
In Ramayana, when Rama and his men tried to cross the ocean to reach Lanka to save Sita from Ravana. He decided to perform Tapas and invoke Lord Varuna. He conducted it for three days and three nights. But there was no sign of Lord Varuna. Rama was upset and angered by the situation. He decided to attack the ocean and dry it up. When Rama started to burn it with flames, Lord Varuna appeared. He said that he would not be able to dry up the sea because of its depth. So, Lord Varuna permitted them to build a bridge that would connect the two lands. Lord Varuna added that he would not cause any hindrance during the process
Hence Varun will lead Ram & Priya later