The Ouroboros is an ancient symbol of transformation and it’s usually depicted in the form of a snake or a dragon swallowing its own tail, in a circular shape.
There are numerous meanings to this symbol. For instance, it generally refers to eternity - to the cyclic process of regeneration; “oneness” - to the autonomous nature of “reality”, devouring itself in the act of continually recreating itself. Order out of chaos. From the beginning to the end, from everlasting to everlasting.
In Egypt (where this symbol was originated), it represented the sun and the travels of the sun disk. In Gnosticism, it was related to the solar God Abraxas, and signified eternity and the soul of the world.
On the other hand, in Alchemy, it represents the spirit of Mercury - the substance that permeates all matter - and symbolises continuous renewal and rebirth, the cycle of life and death, and the harmony of all opposites.