Selena and her followers have arrived on Earth, preparing to bring darkness on Earth, with Kara and Mon-El stranded on Argo. Meanwhile Sam begins to feel negative side effects of being separated from Reign. Meanwhile, J'onn and his father M'yrnn prepare to perform the Reach.
Tropes:
- Alas, Poor Villain: Coville's death evokes some sympathy. Despite having been a deluded fanatic, you can't help but feel a little bit sorry for him, being mercilessly executed by the people towards whom he dedicated everything and loyally did all of their biddings.
- Back from the Dead: Reign is resurrected in this episode.
- Batman Gambit:
- Supergirl uses the hologram of her mother to trick a Dark Priestess into activating the portal and bringing her, Mon-El, and her mom to Earth.
- Turns out that Selena giving Kara the Harun-El two episodes ago was part of one to separate Reign from Sam.
- Cliffhanger: The episode ends with Selena beginning the Hostile Terraforming of Earth. J'onn and M'yrnn prepare to enact a risky plan to hold the Earth together while Supergirl and the others stop the Dark Kryptonians and Reign.
- Dying Moment of Awesome: Though we'll have to wait for the season finale to actually see it, it's pretty clear that M'yrnn shapeshifting into the Earth, spreading his power out at the nexus point of the Hostile Terraforming, will be both the ultimate method of saving the Earth, and the ultimate sacrifice for M'yrnn.
- Face Death with Dignity: M'yrnn, who is completely calm during the ceremony and later doesn't hesitate one bit while planning a Heroic Sacrifice for Earth.
- Fantastic Racism: When Selena decides to get rid of Coville, Coville turns to Reign and questions how she can allow such injustice when he's been loyal. Selena then explains that Reign's justice is for them, not for humans.
- Heroic Sacrifice: M'yrnn decides to use his shapeshifting powers to meld with the Earth and fight the terraforming, even though this would almost certainly kill him and prevent him and J'onn from completing the Reach.
- Hostile Terraforming: The Dark Priestesses intend to use Reign to terraform Earth into a new Krypton.
- Idiot Ball: Kara could merely smash the vials of blood with her hands but instead opts to throw them in the air to heat-vision them. This allows Selena to catch the left-overs.
- Literal Split Personality: The Dark Priestesses are able to use a ritual to revive Reign apart from Sam, though they remain connected.
- Love Is a Weakness: Selena says as much.
- Long Game: The Worldkiller cult has been planning their takeover of Earth for decades.
- Mauve Shirt: Agent Demos, a recurring extra, gets killed by the Dark Kryptonians.
- Motive Rant: Selena leaves behind a hologram recording of a very spiteful message about how her Religion of Evil was condemned by Krypton, and she had to hide it for years.
- My Greatest Failure: Winn sees Demos dying in spite of his technology as this.
- Out of Focus: James, once again, who appears in only one short scene, comforting Winn about Demos' death.
- The Reveal:
- Why did Selena give the Harun-El to Kara? To separate Reign from Sam so the latter could no longer weaken the former. She thought it was "quaint" that Kara assumed Sam would be the one to survive.
- Reign's power comes from a fountain in the Dark Valley that provides infinite strength, explaining how normal Kryptonian rules do not apply to her.
- Synchronization: Sam and Reign are connected despite their separation. As Reign grows in strength, Sam weakens. However, it's posited the reverse may also be true, so Sam travels back to the Dark Valley to find the source of Reign's strength and take it for herself.
- Terrible Trio: The three Dark Priestesses.
- Ungrateful Bastard: Even after the perfectly loyal Coville did all of their biddings, the Dark Kryptonians don't hesitate one second when they condemn him to death.
- Visionary Villain: Selena and her sistren intend to terraform Earth into a new Krypton.
- The Worf Effect: Winn's new portable shield technology, which doesn't stop the Dark Kryptonians from throwing him around and murdering Demos.
- You Are in Command Now: Alex is made Director while J'onn takes a leave of absence to perform the Reach, the Green Martian death ritual, with M'yrnn.
- You Have Outlived Your Usefulness: Selena kills Coville when they have no further use for him.
