The episode introduces the , a prehistoric type of Zoroastrian demon that is invisible except for its shadowy silhouette on walls.
: This is considered a "Wham Episode" by reviewers because it confirms that the thing that killed Mary Winchester is a demon and establishes that John is actively hunting it. ShadowSupernatural : Season 1 Episode 16
"Shadow" is most notable for the long-awaited reunion with . The episode introduces the , a prehistoric type
: Keen-eyed fans have pointed out that while Sam and Dean are covered in severe razor cuts from the Daevas at the end of the episode, their skin is perfectly clear in the very next episode, "Hell House". : Keen-eyed fans have pointed out that while
: The reunion is cut short by a final Daeva attack, leading to a realization: Meg was right—John is vulnerable when he is with his sons.
: After being captured, Sam and Dean manage to free themselves and turn the Daevas against Meg, leading to her being thrown out of a high-story window (though she survives due to her demonic nature). Family Reunion and Bittersweet Parting
: Critics note that the episode heavily uses "noir" elements, where the literal shadows on the wall represent the metaphorical darkness of the Winchester family's past.