Season 4 of Supernatural started with the breaking of the first of the 66 seals that needed to be broken to allow Lucifer to walk the earth, and it ended with the last of those 66 being destroyed. Dean broke the first by being a righteous man spilling blood in hell, and Sam broke the last (which turned out to be Lilith herself) by killing her. Sam was the one to take the action that opened the door to Lucifer's cage, but if we step back and look at the entirety of the process one could argue that Dean's breaking of the first seal was actually worse. Why?
1. Because it started the domino effect. It seemed that the seals started breaking faster and faster as the season moved along once this first seal was broken.
2. Because what he did to break the first seal was self-serving. It was totally understandable considering what he was going through, but still self-serving.
3. Even though Sam was trusting and being tricked by a demon, he honestly thought he was doing the right thing and preventing the apocalypse. He was even willing to sacrifice himself to Lilith if it prevented Lucifer rising.
Though I am not a theology expert, I don't believe the 66 seals are real. But the concept of seals in Christianity is familiar and a good jumping-off point for creating a fictional storyline because of that familiarity and unease about it. The opening of the seven seals is included in the Book of Revelation and signal the End Times (must like the 66 do in the Supernatural world). The first four (Conquest, War, Famine, Death) are identified with different color horses and are more commonly known as the Four Horses (or Horsemen) of the Apocalypse. They are followed by the Vision of Martyrs (a vision of those slain for the Word of God), Great Earthquake/Visions in Heaven/Marking of the 144,000 servants of God, and Trumpets of Angels/End of the World.
I think stories that are tied even in the loosest way to one of the modern theologies make people more uncomfortable than stories that couldn't possibly be real (vampires, werewolves and djinn, oh my!). Perhaps that's why this season has been a bit uncomfortable while also being incredibly awesome.
Do you all feel the same way about stories which draw on Christianity or other modern religions?