Lilith

Lilith was a powerful demon and Lucifer's second-in-command. She was the very first human to be turned into a demon. In fact, she was the very first demon that Lucifer ever created after Michael cast him out of Heaven and was thrown into Hell. Lucifer twisted and warped her soul as a way to mock God's most beloved creation: humanity, resulting in Lilith not becoming a demon in her own right but also the final Seal, meaning that with her death Lucifer himself would be released into the world.

She is a feared and ruthless demon. Though, she prefers her hosts to be young girls, she's been known to possess beautiful women in order to fool or seduce men. As she was the first demon created, she therefore became the final seal to release Lucifer from his prison in Hell.

Background
Prior to the start of the series, a Crossroad Demon would cross paths with Bela Talbot. The demon made a deal with Bela: the demon would kill Bela's parents (Bela's father being abusive and her mother pretending that everything was fine) and guarantee Bela a large inheritance from their deaths in exchange for her soul ten years from the day they made the agreement. In the end, it would be Lilith who would hold this contract, amongst others (she holds Dean's).

Season 3
In "Jus In Bello", it is revealed by Ruby that Lilith is the one that sent a horde of thirty demons to kill the Winchester brothers after they are captured by Special Agent Victor Henricksen and being held in the local sheriff's office. Ruby further explains that Lilith is more interested in killing Sam due to t he fact that she sees him as competition. After the Winchester brothers successfully defeat the horde of demons and Henricksen lets them go, Lilith makes her first appearance. She arrives at the sheriff's office possessing a little girl accompanied by an adult woman, most likely possessed by a demon. Lilith walks over to Nancy Fitzgerald, the secretary of the sheriff's office, and tells her that she's looking for two boys and that they're brothers, "one's really tall" and "one's really cute". Nancy asks what Lilith's name is. Lilith tells her that her name is "Lilith" and then reveals her white demonic eyes. Before, Nancy, Henricksen, or the deputy could do anything, Lilith raises her hand releasing a burst of white energy causing everyone in the sheriff's office to scream in agony. Later on, Ruby has the Winchester brothers turn on the news to see that Lilith not only killed everyone in the sheriff's office but blew up the building as well.

She then makes her second appearance in the season finale, "No Rest for the Wicked". She is shown to be on "shore leave", taking possession of a young girl and taking her family hostage in their home in New Harmony, Indiana. She forces them to treat her as their daughter, making sweets and deserts for her and playing with her, lest they should be killed for making her unhappy. The Winchesters track her down, and infiltrate the house, ready to kill the girl, only to realize that Lilith isn't possessing her. As the Hellhounds draw near to kill Dean, Ruby offers to keep them at bay with the Demon-Killing Knife, but as Sam hands her the knife, she reveals that she is actually Lilith. After the Hellhound kills Dean, Lilith tries to use her powers to personally kill Sam, but, to their shock, he is immune. As Sam charges to attack her, she leaves the body she is possessing and escapes.

Season 4
Lilith returns in the Season 4 episode as a hallucination that Dean has after catching a "ghost sickness" that plays on the victim's fears. Then later Lilith appears "The Monster at the End of This Book", this time in the body of a "comely dental hygienist", in order to seduce Sam into sacrificing himself and Dean in exchange for her stopping all of her efforts to break the 66 Seals.

Later in the final episode of the season, Lilith waited at St. Mary’s Convent in order for Sam to kill her in order to break the last seal in order to release Lucifer free from his cage.

When Sam actually did kill her, the blood from Lilith's mouth spread around in a circle, forming a portal for Lucifer to emerge from.

Personality
Like most demons, Lilith serves to manipulate others for her own ends, even taking a human body, preferring young women and girls as her unwilling hosts.

She even has something of a sadistic nature when it comes to slaughtering or killing others. She also likes to torture and kill others, sparing no guilt and has no mercy for causing their deaths.

She seems to regard her followers as nothing but as means to an end as seen in "Lucifer Rising", when she mercilessly sacrifices some demonic-possessed people who are standing guard in an empty church as a part to bring Lucifer into the world.

Relationships

 * Lucifer (Creator, Leader)


 * Crowley (Second-in-Command, Lover)


 * Demons (Subordinates)

Powers
Lilith, being a white-eyed demon, is extremely powerful. She was one of two white-eyed demons that the Winchester brothers had ever seen, the other being Alastair. While she seems to be no unafraid of normal angels, she has shown that she is afraid of archangels. She has shown the following powers:
 * Demonic Possession - As a demon, Lilith can possess human beings, but she mostly likes to possess young girls. Sometimes, she possesses young, attractive women.


 * Telekinesis - Lilith has porven to have amazing telekinetic abilites. She can pin people to walls and break a human's neck without touching it.


 * White Energy Blasts - Lilith can emanate a demonic white energy blast from the palm of her hand that can destroy humans and other beings.


 * Reality Warping - Like a crossroads demon, Lilth can grant human's wishes if a deal is made. She also holds of the souls deals.
 * Control Over Hellhounds - Lilith has shown that she has complete comand over Hellhounds and she can force them to do what ever she wants.
 * Teleportation- Lilth has proven that she can travel and appear anywhere in the world by teleporting to the locations she wants to be at.
 * Invulnerability - As being the first created demon, Lilth is a very difficult demon to kill. It's proven that she is invulnerable to weapons that could harm or repel most demons. The only things that can kill Lilth are arca-angels, the Colt, or Special children that have demon's blood and has the power to kill demons. Lilth's death, however, gave Lucifer the freedom to walk the earth and leave his prison.

Season 3

 * "Jus In Bello"
 * "No Rest for the Wicked"

Season 4

 * "Yellow Fever"
 * "The Monster at the End of This Book"
 * "Lucifer Rising"