(/ˌjʊərəˈbɒrəs/; /ʊəˈrɒbərəs/]; Greek: οὐροβόρος) is an ancient symbol depicting a serpent or dragon eating its own tail. Originating in Ancient Egyptian iconography, the ouroboros entered western tradition via Greek magical tradition and was adopted as a symbol in Gnosticism and Hermeticism, and most notably in ALCHEMY.
-Wikipedia

Symbolizing eternity and endless, unbreakable cycle of to polar opposites whether it be life and death, dar and night or GOOD AND EVIL.