In the Milky Ocean of Vaikunth Dham, the Supreme Being Bhagwan Vishnu rests on the thousand headed serpent Seshnaag while Bhagawathi Lakhsmi presses his feet. Seshnaag is a representation of energy and Bhagwan Vishnu is the soul of the energy. Hence, Bhagwan Vishnu while resting on the Seshnaag depicts that the energy and soul are manifested within him and together they protect the worlds.
Sesh means which remains, and thus Seshnaag signifies the one which remains after the whole world perishes. While Brahma sleeps, Bhagwan Vishnu rests on the Sesh Naag waiting for the next Kalpa to start. When the time of a new Kalpa comes, a new Brahma is born from the navel of Bhagwan Vishnu and thus creation starts again. Al through this great process, Seshnaag remains alert along with Bhagwan Vishnu preserving the good things to be carried forward to the next Kalpa.
Seshnaag is also called as Adi Sesha and Ananta Sesha meaning the first, or the endless one. He is the King of the Nagas (serpents) and the eldest son of Rishi Kahsyap and Devi Kadru. Nagalakshmi is his consort, while Sulochana, wife of Indrajeet is his daughter.
Sesh Naag’s brothers who were the other sons of Kadru had great rivalry with Garud which Seshnaag was against. He left his cruel brothers for good and went to the Gandhamdan Mountain and did penance for several years. Brahma Ji was pleased with his devotion and asked him a boon. Sesh Naag requested that he wanted a pure mind which could be kept in control and be stable all time. Brahma Ji was very pleased by this and told him that one such place which could give him that bliss was Vaikunth Dham and asked him to serve Bhagwan Vishnu by offering him his coils as a bed. Seshnaag gladly agreed and thus became the constant aid of Bhagwan Vishnu.
Once when Mother Earth became unstable, Brahma Ji requested Seshnaag to go underneath her and stabilise her by offering her support. Thus, Seshnaag went to the Patal Lok (Neither World) and balanced Mother Earth on his hood since then helping Mother Earth regain back its stability.
Seshnaag was not only the bed on which Bhagwan Vishnu laid but also, duly assisted Bhagwan Vishnu in performing his role of retaining Dharma along with his swami, whenever the purpose called for. In the Ram Avatar, Seshnaag incarnated as Lakshman, the younger brother of Shri Ram. The incarnation of Lakshman is one of the greatest examples of selfless service of brotherhood love. Immensely gratified with Lakshman’s endless services, Shri Ram says that he would return back the favour by becoming his younger brother in the next avatar and thus Seshnaag is born as the elder brother Balram in Krishna Avatar. Shri Krishna serves him dutifully as his younger brother thus keeping up the word of Shri Ram. While Lakshman was the bearer of the great bow and arrow, as Balaram, he carried the Hal (plough) as his weapon and thus introduced new agricultural techniques to mankind.
Being the constant companion of Bhagwan Vishnu and very dear to him, it is hence Bhagwan Krishna states in his Geeta to Arjun that, of the serpents, he is the Seshnaag, signifying his affection and importance to all the worlds. Whenever one visualises Bhagwan Vishnu, it is the divine figure of him resting on the Seshnaag which first flashes in mind making him the most divine creations of the creator.