Nāga

Nāga (नाग) is the Sanskrit word for a deity in the form of a very great snake (specifically the King cobra), found in Hinduism and Buddhism. The use of the term nāga is often ambiguous, as the word may also refer, in similar contexts, to one of several human tribes known as or nicknamed "Nāgas"; to elephants; and to ordinary snakes, particularly the King Cobra and the Indian Cobra.

Sesha Naga

In Hindu mythology, Seshanaga or Shesh Nag (also known as Ananta) is a massive serpent that floats coiled in space, or on the universal ocean, to form the bed on which Vishnu lies. He is one of the primal beings of creation, and is closely associated with Vishnu. His name means "that which remains", from the Sanskrit root shiş, because when the world is destroyed at the end of the kalpa, Shesha remains. Occasionally, Shesha is shown as a five headed snake. But in his real form he has 1000 heads with each one wearing a crown.

Sesha is referred variously as Adisesha (the first Sesha), or Anantasesha (Endless Sesha). According to H. P. Blavatsky:

Sesha-Naga, the King of the “Serpent” race, is synonymous with Ananta, the seven-headed Serpent, on which Vishnu sleeps during the pralayas. Ananta is the “endless” and the symbol of eternity, and as such, one with Space, while Sesha is only periodical in his manifestations.