Lilith is the very first demon that Lucifer created to "get back" at God. She was buried at the very deepest parts of hell until the devils gates were opened. She is very powerful and cannot be killed but the demon knife. She was trying to break the 66 seals to free Lucifer from hell. She eventually breaks 65 of them and the Sam kills her (weird demon powers) but he doesn't know that she is the 66th sello (Lucifer's first demon) and then Lucifer is released from hell.
