[s4e21] When The Levee Breaks -

: Ruby reveals that Lilith is "Lucifer's first" demon and that only she can break the final 66th seal.

: Faces internal conflict after being ordered to sabotage the brothers' efforts, ultimately capturing Anna Milton when she confronts him about his actions. Lore and Production Details [S4E21] When the Levee Breaks

: Portrayed as a "villain protagonist" struggling with a supernatural addiction he believes is necessary to kill Lilith and stop the apocalypse. : Ruby reveals that Lilith is "Lucifer's first"

: Dean tracks Sam to a motel, leading to a violent brawl. After Sam nearly strangles him, Dean delivers a final ultimatum: if Sam walks out the door, he should never come back. Sam leaves, effectively severing their bond as they head into the finale. Major Character Dynamics : Dean tracks Sam to a motel, leading to a violent brawl

: Directed by Robert Singer and written by Sera Gamble. It is one of only three episodes in the entire series where no characters die.

" When the Levee Breaks " is the 21st episode of Supernatural 's fourth season and the 69th episode overall. Premiering on May 7, 2009, it serves as the penultimate episode of the season, directly setting the stage for the apocalypse.

: The title is a nod to a 1929 blues song famously covered by Led Zeppelin in 1971.