Saint Ruru is a hermit famous in the Hindu Puranas.

According to Devi Bhagavata (Skandha 2), Puloma was the wife of Bhrgu. He got the son Chyavana

Chyavana

Chyavana was a maharshi in Hindu mythology. He was son of sage Bhrigu and known for his rejuvenation after penances for several years. According to the Mahabharata, he was powerful enough to oppose the Vajra of Indra and was responsible for the Ashvins getting their share of the sacrificial...

 by Puloma. Chyavana married Sukanya

Sukanya

In Hindu mythology, was the daughter of Shryayati, son of Vaivasvata Manu and the wife of the great sage Chyavana.The sage had spent so long in meditation that he was covered by a termite nest. The beautiful girl Sukanya came upon the nest and saw two shining objects inside...

. Pramati was born to them. The hermit Pramati married the beautiful damsel Pratapi and got a son named Ruru. He grew up to become a famous hermit.

Ruru happened to encounter exceedingly beautiful Pramadvara, the daughter of Visravas

Visravas

Visravas is the son of Prajapati Pulastya in Hinduism. According to a statement of the Mahabharata, he is a reproduction of half Pulastya himself....

 and Menaka

Menaka

In Hindu mythology, Menaka is considered one of the most beautiful of the heavenly Apsaras.She was sent by Indra, the king of the Devas, to break the severe penance undertaken by Vishwamitra. She successfully incited Vishwamitra's lust and passion when he saw her swimming naked in a lake near a...

 and momentously fell in love with her. The father of Pramadvara came to know of this and decided to give her in marriage to him. During the marriage preparations, Pramadvara was bitten by a snake and fell down dead.

Ruru was greatly sad and disappointed. By his determination and sacrifising half of his life to her, Pramadvara came to life again and Ruru married her.

Accodging to Mahabharata

Mahabharata

The Mahabharata is one of the two major Sanskrit epics of ancient India and Nepal, the other being the Ramayana. The epic is part of itihasa....

 (Adi Parva), Ruru developed relentless hatred against serpents. He wandered about destroying every serpent he came across. Finally he confronted Dundubha, he was given exhortations and good advices regarding righteousness. Saint Ruru had taken a lively interest in the sacrifice of Janamejaya

Janamejaya

Janamejaya was a Kuru king. He was the son of Parikshit and Madravati. He was the grandson of Abhimanyu and the great-grandson of Arjuna, the valiant warrior hero of the Mahābhārata. He was ascended to the Kuru throne following the death of his father. His significance comes as the listener of the...

meant for the extermination of Serpents.