- For the character this episode is based around, see Samantha Arias.
- "Who is she?"
- "World Killer. The one who will bring about the end of times. This is your purpose, to fight the Devil."
- —Kara Danvers and Thomas Coville
Supergirl investigates a mysterious symbol popping up all over National City, tracing its origins back to an ancient prophecy and the mark of the World Killer, Reign. Meanwhile, the tension between Lena and Morgan Edge continues to build, causing James to step in and offer up some protection, and possibly igniting a spark in the process.
- After Edge claims that he likes to spread company cheer, James quips "bah humbug", a phrase spoken by Ebenezer Scrooge in the Charles Dickens novella A Christmas Carol.
- J'onn wishes Winn to play "Jingle Bell Rock" by Hall & Oates in order to introduce his father to them. The Legends played the same song for Jefferson's Farewell Christmas Party in "Beebo the God of War" which aired the next day.
- After M'yrnn mentions the Martian holiday Life Day, Winn incorrectly believes that he is speaking about The Star Wars Holiday Special, in which Princess Leia sings a song to the tune of the Star Wars theme.
- After Winn suggests that he has no idea what Star Wars is, J'onn claims the 1980 film The Empire Strikes Back to be the best film sequel of all time.
- Reign's heat vision is red, a reference to the traditional color of Kryptonian heat vision.
|Supergirl season 3|
|"Girl of Steel" • "Triggers" • "Far From the Tree" • "The Faithful" • "Damage" • "Midvale" • "Wake Up" • "Crisis on Earth-X, Part 1" • "Reign"|
|"Legion of Super-Heroes" • "Fort Rozz" • "For Good" • TBA • TBA • TBA • TBA • TBA • TBA • TBA • TBA • TBA • TBA|