Here is a little excursion into Gnostic thought. According to Gematria (Qabalistic numerology) the Hebrew words Nachash (Serpent) and Messiah are equivalent. In the Garden of Eden, the Nachash attempts to help Adam and Eve by offering Eve the fruit of the Tree of Knowledge (thus elevating them above the animal level). However, this results in the Demiurge (Jehovah) banishing them from the Garden out of fear of their new power. The Nachash later reappears, transformed into the Messiah (Christ), whose mission is to teach humans the way back to Paradise through Enlightenment. He is executed by those who do not understand his mission, the method of execution being the Cross (Tree of Life). The attachment is a representation of both the Nachash on the Tree of Knowledge and the Messiah on the Tree of Life (Cross).
There is also an attachment showing the Serpent having ascended the Sephirotic Tree, as mentioned by Eeviee.