Thor's hammer Mjolnir made its first appearance on Supernatural since season eight, and fans are loving it. During tonight's episode, "The Last Holiday," there's an epic shot of Sam Winchester (Jared Padalecki) wielding the hammer during a battle. The specifics of the battle are not clear, as the shot came in the middle of a montage of such showdowns with monsters of all shapes and sizes -- but the hammer, which has been established as a weapon powerful enough to kill deities, was used to do just that in the season eight episode "What's Up, Tiger Mommy?" in which Sam used it to mete out some cosmic justice.