The team travels into the far future to a fatal point in Savage's rise to power.
Tropes:
- Always Someone Better: At the end of the episode, Mick and Snart have a fistfight to decide what happens to the former. While they might have been evenly matched in 2016, Mick's training at the hands of the Time Masters lets him quickly take control of the fight and beat the daylights out of Snart. In addition, Mick spares Snart and stays with the team, not because he's realized the error of his ways but because the Time Masters have sent something worse than him to finish the job and there's safety in numbers.
- Analogy Backfire: For Vandal Savage, the legend of Oedipus is an inspirational tale about a man who murdered his father to become a great and powerful king. He leaves out the fact that Oedipus killed his father by accident, won the crown of Thebes by defeating the Sphinx and especially that it didn't end well for him. The twisting of the tale is likely deliberate on Savage's part; he only really needs one element of it to sink in for his plans to work, with the rest of the story being pure manipulation.
- Badass in Distress: Sara was briefly captured by Savage in the climatic battle.
- Bad Future: For starters, corporations now double as federal governments - even in Central City. And outside of Kasnia, the whole world is an overpopulated, poverty-ridden mess, with repeated mention of food riots. (And the only reason Kasnia is stable is because it's a Police State.)
- The Bad Guy Wins: At the end of the episode, everything works out in Savage's favor; he has control of the Kasnian Conglomerate and the Armageddon virus to aid his plans, he's well-positioned to rid himself of Per Degaton when he's outlived his usefulness, and he has a base of operations for his future campaign of world domination.
- Bilingual Bonus: Intentionally or not, Kasnia sounds similar to "kaźnia", an old Polish word for execution.
- Breather Episode: for the Arrowverse as a whole, given that it airs the day after one of the most dramatic Arrow episodes of all time, "Eleven Fifty-Nine". For that matter, it's this in the context of Legends as well, coming after a string of far more serious and dramatic episodes. That being said, the ending isn't exactly sunshine and rainbows.
- The Bus Came Back: Carter and Prof. Boardman both return in flashbacks.
- Call-Back: Per Degaton was first mentioned by Rip in the first episode.
- Canon Foreigner: Ray has no brother in the comics.
- Continuity Nod: Gideon mentions a sexual dream Sara had about a nurse.
- Curbstomp Battle: When Gideon shows Savage's coup against Per Degaton, Vandal easily kills an armoured Degaton in two knife moves. To further cement how mighty Savage is, offscreen he defeats Sara without breaking a sweat.
- Demoted to Extra: In the first two episodes, Falk Hentschel's name was part of the main credits. Here, he's only billed in the guest star lineup, not with the "Special Guest" citation like the guesting former cast members of the other Arrowverse shows. Possibly justified since Carter only appeared in flashbacks.
- Downer Ending: The Legends failed to prevent Savage from using Per Degaton to advance his own power. If anything, they made matters worse, as Savage manipulates Degaton into murdering his father, then uses his new influence over the Kasnian Conglomerate to unleash a deadly virus that devastates the world's population five years earlier than it had before the timeline changed. Besides which, the team's efforts to forestall Savage's rise to power didn't do a thing to change the timeline. On top of all that, with Mick having failed to capture the team, the Time Masters have dispatched an even deadlier group of assassins whose mission is explicitly to kill them.
- The Dreaded: The Hunters, which the Time Masters will now send upon the Legends, are so terrifying that the only advice Mick is able to give the team is to run.
- Elite Mooks: After easily facing down terrorists with 20th century guns a few episodes back, the team almost lose against the ATOM robots that can fly and counter the team's powerful energy attacks with their own lasers.
- Even Evil Has Loved Ones: Tor Degaton chooses to let the team go rather than risk his son's life.
- Even Evil Has Standards:
- Mick commented that there's nothing heroic about killing a child. Somewhat hypocritical though, as he intended to kill Snart's sister during all possible stages of her life last episode.
- Tor Degaton, although he's the head of an oppressive Police State, flat-out refuses Savage's suggestion of "culling the herd" (with the "herd" being the overpopulated outside world). This gets him assassinated by his own son.
- Evil Mentor: Savage serves as this to young Per Degaton.
- Gone Horribly Wrong: What happens to Ray's ATOM technology — what was meant to help people is instead perverted to help in authoritarian oppression.
- Hard Truth Aesop: Ultimately, not killing Per Degaton proves to be more harmful; the Armageddon virus is released and most of the world is wiped out, which could have been avoided had they killed him.
- Hazy-Feel Turn: With a hint of Enemy Mine; since he failed to capture the Legends for the Time Masters, Mick is as much a target for the Hunters as they are, so he aligns with them to stay on the run and stay alive.
- Hitler's Time Travel Exemption Act: Most of the team is deeply uncomfortable with killing an innocent child even if he's destined to be a dictator. However, Per Degaton isn't that innocent thanks to Savage's teaching—he's like something out of a Nazi Youth Camp.
- Horrible Judge of Character: What kind of father hires Vandal Savage as a personal tutor for his son!? This is apparently a family trait; Per Degaton refuses to believe that Savage would ever betray him. One imagines that his death came as something of a surprise.
- If You Kill Him, You Will Be Just Like Him!: Stein warned Hunter that killing an innocent child before he becomes a dictator is no better than Vandal Savage's atrocities.
- It's All My Fault: Rip tries to get through to Mick by saying that he's responsible for bringing him along, and Mick shouldn't have any quarrel with Snart. Mick replies that he's just gonna kill both of them anyway.
- Let's You and Him Fight: Mick and Snart finally blow off some steam, literally.
- Love Is a Weakness: Per Degaton, clearly influenced by Savage, expresses views to this effect, referring to his father as weak, and seeming disappointed that Tor was willing to spare the Legends in exchange for his son's life.
- The Man Behind the Man: Savage to both father and son Degatons, at least until Savage decides to step up to the front.
- Nice Job Breaking It, Hero: Thanks to the team's meddling, Savage's rise to power is actually sped up by five years. The only bright side is that they deprived him of ATOM drones, but he wasn't using those much anyway.
- No New Fashions in the Future: Subverted in so far as while the fashion is just what you'd expect in your average dystopian police state, there are no new textiles in the future. The clothes are still simply made out of wool, much to the annoyance of Jax.
- Puppet King: Per Degaton for Savage. Helped by the fact that the boy's underage so Savage gets to act as his proxy.
- Putting on the Reich: The Kasnian uniforms bear an uncomfortable resemblance to Nazi uniforms, although the Kasnian Conglomerate, while oppressive, is presented as a lesser evil than Vandal Savage. Until he takes over, at least.
- Red and Black and Evil All Over: The uniforms of Kasnia's military.
- The Reveal: Mick reveals that since he failed to bring in the team, the Time Masters have sent the Hunters — time-traveling robots to erase the team from history.
- Rousseau Was Right: Subverted. One act of mercy isn't enough to counter a lifetime of conditioning on Per Degaton.
- Sadly Myth Taken: Invoked; Savage presents the story of Oedipus to Per Degaton as a young prince triumphing over his father and taking his throne, omitting the various subtle details that caused this chain of events in the original myth.
- Secret Police: The automated ATOM suits function as this.
- Self-Made Orphan: Young Per Degaton kills his own father under Savage's suggestion.
- "Shaggy Dog" Story: The team goes to 2147 to make sure Per Degaton doesn't help Vandal Savage's rise to power...unfortunately, all they do is cement it.
- Shout-Out: Ray's alias is Dr. Hannibal Lecter.
- Sibling Rivalry: Turns out Ray has a brother named Sidney, and they don't get along.Ray: He allowed my tech to be perverted by the defense industry! That is so Sidney.
- The Social Darwinist: Savage compares reducing the population of Earth to culling a herd.
- Terminology Title: "Progeny" means a descendant or the descendants of a person, animal, or plant; offspring.
- Additionally though, the title could also refer to Per Degaton, son of Tor Degaton.
- Too Dumb to Live: Genetic tracking and ATOM robots executing a guy who stole someone's purse are meant to show how nasty Police State Kasnia is, but if Kasnia has genetic tracking and flying robots that will kill you on the spot if you break the law, how stupid you must be to actually try to steal someone's purse in broad daylight?
- Trailers Always Spoil: A few weeks before the episode aired, the trailer for the second half of this season showed Per Degaton preparing to kill someone in their sleep (his father). This scene does not happen until the end of the episode, meaning that whilst watching, it was easy to guess the result of the team's attempt to prevent the Bad Future.
- Unreliable Narrator: Rip tells the Team that 2147 was considered the pinnacle of human civilization. Yet later, we learn that outside of Kasnia there are huge problems with famine and overpopulation, and corporations are running most of the planet.
- Weirdness Censor: Dr. Bryce is only mildly bemused that Ray looks exactly like a bust of the founder of her company.
- Welcome Back, Traitor: Mick is back on the team by the end.
- Well-Intentioned Extremist: Tor Degaton, while being the ruler over a police state, still seems to have some standards and a sense of honour. It's what Vandal and his son see as a weakness.
- What Measure Is a Mook?: The team has no problem killing Kasnian soldiers.
- What You Are in the Dark:
- When it comes down to it, Mick can't bring himself to kill his best friend.
- Unsurprisingly, Rip can't bring himself to kill Per Degaton.
- Would Hurt a Child: The main conflict of the episode. Snart advocates killing the young Per Degaton, while most of the team objects. Rip eventually tries to execute Degaton for the sake of preventing Savage's rise to power and the death of his own son. Ultimately, Rip finds that he can't bring himself to kill the boy.
- You Have Failed Me: Since Mick failed to bring in the Legends, he's as much of a target for the Hunters as they are.
- You Have Outlived Your Usefulness: According to Rip, after Savage uses Per Degaton to conquer the world, he kills him in order to take the throne for himself.
- You Wouldn't Shoot Me: Per Degaton tells this to Rip at gunpoint because Savage taught him to recognize a killer. He's right and Rip decides to spare him.
