text: In the Bhagavata Purana, Shesha is named Sankarshana, the tamasic energy of Narayana himself, and is said to live deep within the inner layers of Patala, where there are many serpents with gems on their heads and where he reigns as its ruler. He is said to have existed before the creation of the universe. When the universe is towards its end, he creates the 11 Rudras from the serpents to destroy the universe for a new one to be created.
  Sankarshana is also one of the four vyuhas, or primitive forms of Vishnu, the other three being Vasudeva, Pradyumna, and Aniruddha.
  In Gaudiya accounts, Sankarshana expands himself as Garbhodakshayi-Vishnu in the beginning of the universe to create Brahma. In other words, Sankarshana is believed to be Narayana himself.
  In the first few chapters of the Puranas, it is also said that Sankarshana preached the Bhagavata to the Four Kumaras, who in turn passed on this message. At some point, the message was passed to sage Maitreya, who in turn preached it to Vidura.
  Marriage
  According to legends, Shesha is married to Nagalakshmi. As per the Garga Samhita, she is considered to be the personification of the divine ocean called the Kshira Sagara.