The serpent is a very complex and meaningful symbol. It is chaos, the darkness, the unknown. The snake is not evil in itself, but it needs te be transcended. The darkness needs to become light. The unconscious needs to be made conscious. The shadow needs to be integrated. That’s why the serpent also symbolizes transcendence or transformation; it always changes its skin. The serpent is Satan, but it is also Christ. It is the dead hero in the underworld. But it is also the mysticism of the mother that strangles or poisons her child. But she can also save your life, since she is the source of life. If you swallow the snake, that means that you become one with the mother. It is the mother libido (libido = psychic energy) that needs to be sacrificed in order to create the world. This we can see in the Mesapotamian mythology, when Marduk defeats the dragon/serpent Tiamat and created the world from her body.
The snake symbolises death, as well as eternal life. The serpent is the soul of death and when it castrates someone, that means ultimate death. It is therefore the guardian of the underworld, and thus, the guardian of the treasure, the gold. Gold is only to be found deep in the earth. That is, valuable things are only to be found in the unconscious. It is time that devours us and transcending the serpent ultimately means transcending time, and therefore, death. When you transcend the snake, you will become immortal. Jesus on the cross is the serpent that was transcended. He compares himself to the serpent in the desert that was transcended by Moses. As Moses lifted up the serpent, so must the son of man be lifted up, so whoever believes in Jesus will have eternal life. (John 3:14-15). When Moses lifted up the snake, everybody who dared to look at it would live.
We find the serpent in many symbols, art and myths: the dollar sign, the medical sign, the Christmas tree, the rod of Hermes, Aion, Zurvan, Phanes, the Orphic Egg and much more.