* The Yellow-Eyed Demon: Azazel is the primary antagonist of Supernatural's first season. He was responsible for the death of Mary Winchester, and he is a powerful demon seeking to open the gates of Hell.
* The Colt: In the season finale, Dean Winchester, armed with the legendary Colt, finally kills Azazel. However, this isn't the end of the demon's story.
* The Devil's Trap: Azazel was bound to a devil's trap by the hunters before being killed. It's implied that the Colt's bullet simply "disabled" Azazel, and that he may still be alive, although trapped and unable to escape.
* The Apocalypse: Later seasons reveal that Azazel was a key player in the events that led to the Apocalypse. He played a role in raising Lucifer and was a significant force in the demon army that attacked the world.
* The Empty: Eventually, Azazel's powers were absorbed by the Empty, a powerful entity that feeds off the souls of demons. He became a part of the Empty's being, further blurring the lines of his existence.
In essence, Azazel's fate is a bit of a mystery. He's not truly "dead" in the traditional sense but exists in a sort of limbo within the Empty. While he hasn't been seen in the show since the first season, the potential for his return always exists, especially considering the supernatural world's unpredictable nature.