Lilith's vessel

Lilith's vessel was an unnamed woman who acted as the final vessel for the first demon Lilith.

The Monster at the End of This Book
After meeting Prophet Chuck Shurley, Sam and Dean Winchester learn that Lilith is coming after them in this woman's body, someone Chuck describes as "a comely dental hygienist from Bloomington, Indiana." When Sam decides to let Lilith come in an attempt to finally kill her, she tries to make a deal with him to stop breaking the 66 Seals in exchange for the deaths of him and Dean. When Sam's attempts to kill her fail, he apparently agrees to the deal which Lilith states will require sex with her. She tells him that her vessel, who is still alive from her comments, wants Sam too. When the Archangel Raphael arrives to protect Chuck, Lilith flees this woman, leaving her unconscious on the floor of the Winchesters' motel room.

Lucifer Rising
By the time Lilith goes to St. Mary's Convent to sacrifice herself in order to break the last seal and free Lucifer from his cage in Hell, she has reclaimed this woman as her vessel. When Sam kills Lilith with his powers, the woman dies too and the demon blood that comes from her mouth forms the portal into Lucifer's Cage.

Sympathy for the Devil
The woman's body is left lying on the floor of the convent with the body of Ruby's brunette vessel when God transports Sam and Dean to safety on a plane as Lucifer rises. Her body is presumably destroyed with the convent.

Appearances

 * Season 4
 * The Monster at the End of This Book
 * Lucifer Rising