The serpent arose from inside Adam and Eve as a whispering voice which prompted them to curiousity and rebellion, urging them to disobey Yaldabaoth and eat from the tree.
“Then the one who is wiser than all of them, this one who was called “the beast,” came. And when he saw the likeness of their mother, Eve, he said to her, “What is it that God said to you? ‘Don’t eat from the Tree of Knowledge’?”
She said, “He not only said ‘Don’t eat from it,’ but ‘Don’t touch it lest you die.’ “
He said to her, “Don’t be afraid! You certainly shall not die. For he knows that when you eat from it your mind will be sobered and you will become like God, knowing the distinctions which exist between evil and good men. For he said this to you, lest you eat from it, since he is jealous.” 
- ”On the Origin of the World.” The Other Bible. Ed. Willis Barnstone. Harper San Francisco, 1984. 71. [↩]