Whore of Babylon

"She rises when Lucifer walks the Earth. And she shall come, bearing false prophecy."

- Castiel, quoting the Book of Revelations

The Whore of Babylon appears only when Lucifer rises. Once she appears, it is her job to damn all the people she can to Hell (by convincing them to commit acts such as murder). She appears in "99 Problems" where she's posing as pastor David Gideon's daughter, Leah.

As Leah, she pretends to get visions from the angels, and "foretells" where the next demon attack is going to be. She even gives them an "exorcism" that expels the demons. However, she is the one controlling the demon attacks and the exorcism actually means, as translated by Castiel, "You breed with the mouth of a goat" ("it's funnier in Enochian").

Upon discovering her true identity, Dean Winchester kills her using a stake made from the branch of a Cypress tree.

Powers

 * Shapeshifting - She can shapeshift to fool humans. She impersonated Leah, presumably after killing the real one, and took her form.
 * Invulnerability - She can only be killed by a stake made from a Cypress tree found in Babylon. It must be wielded by a true servant of Heaven.
 * Mind Reading - She can read minds, which helps enforce her false Prophet status.
 * Superhuman Strength - She exhibits incredible strength when fighting off Sam and Dean.
 * Demon Control - She can control demons (possibly through authority rather than power).
 * Telekinesis - She can cause objects to move by thought, using this ability in combat, such as pushing Dean away from her when he finds out what she is.
 * Knowledge of Spells - She knew a spell that can harm Angels.

Weakness
She can only be killed by a stake made from a branch of a Cypress tree. This stake can only be wielded by a true servant of Heaven. Pastor David Gideon was initially chosen for this task, but during the confrontation with the Whore, he dropped the stake. Dean picked it up and stabbed her with it. To everyone's surprise, it worked.

Myth
The myth itself is woven into the antichrist story. She is also mentioned in the bible and described by John in Revelation 17. Some scholars believe that the Whore of Babylon is really a large allegorical figure. It is also believed she also represents Rome mostly because of the reference to her siting on 'seven mountains' (seven hills of the city).

Appearance

 * 99 Problems