Krypton Returns is the second Supermancrossover story arc of the New 52 and the direct sequel to H'el on Earth. Starting in October 2013, the story begins in Action Comics Annual #2 and continues through the Superboy and Supergirl titles, concluding in Superman #25. Before any of these issues were released, Superman #23.3, released during Villains Month, served as a prelude and revealed H'El's origin. Its written by Scott Lobdell, Justin Jordan and Michael Alan Nelson.After the events of H'el on Earth, H'El has been sent back in time to the period of Krypton's explosion. Using his knowledge of the future, H'El hopes to save Krypton, but his actions begin to cause great damage to the universe. Superman and his allies travel to the past in order to stop him.
Krypton Returns contains examples of:
Action Mom: Lara. She even attacks Superman, believing him an intruder when he enters the House of El. Superman, who is seeing his mother for the first time, is astonished. She also trained a pre-Supergirl Kara in at least some combat techniques.
All-Powerful Bystander: The Oracle, the cosmic entity that sends the Superman family back in time to stop H'El, is extremely powerful but his species have an Alien Non-Interference Clause. Because of the threat H'El poses to all reality, the Oracle breaks this rule.
Artificial Kryptonian: H'El is revealed to be this in Superman #23.3. He was created from a collection of genetic material gathered all over Krypton's history by Jor-El in an unmanned spaceship to find a planet where the people of Krypton could be safely evacuated to by the time Krypton exploded.
Asskicking Equals Authority: When Supergirl defeats Kon, the clone leader, the clones see her as their leader. They aid her in her fight against H'El.
Body Horror: In the finale, an alternate version of Jor-El aids Superman in his fight against H'El. Jor-El hits H'El with a gas that will break him down to his cells. Not wanting to kill him, Superman stops Jor-El mid-process, leaving H'El horribly disfigured and weak.
Brought Down to Normal: When they are brought to Krypton, the heroes begin losing their powers by being exposed to Krypton's red sun.
Continuity Nod: This serves as the second appearance of the Eradicator, in this timeline being sent after Superboy to keep him from protecting the past Supergirl.
Cloning Blues: Supergirl is sent to the period of a clone rebellion in Krypton's past.
Crapsaccharine World: What H'El turns Krypton into after he takes over. At first, Krypton looks as the pristine and magnificent world it was before its destruction. Later, it is revealed to have a space station in orbit that attacks intruders and at least one of its moons has a slave camp.
Godzilla Threshold: The state that H'El has put Krypton in, along with the death of Dru-Zod, forces Faora to join up with the Oracle to contact the Superman Family to make sure that Krypton is Doomed by Canon, which she considers a Mercy Kill compared to what has happened to the world.
Heroic Sacrifice: Superboy does not make it to the end of the event alive, and thus Jon Lane Kent, the evil future son of Superman, will headline his book and take his spot on the Teen Titans. He notices that the anti-gravity of the city of Argo isn't strong enough to break the city free from Krypton's gravitational pull, so he uses all his power to give the city and Supergirl's rocket the push they need to leave Krypton's atmosphere. The effort expends all of Superboy's power and he expires in the wake of Krypton's destruction, happy with the great deed he's done.
Meanwhile, in the Future: In Supergirl #26, H'El travels to Superboy's mission's time, while "simultaneously" fighting Supergirl, with the times synching up so that he is hit by multiple Super Family members at the "same time".
When Superman begins to lose his powers due to red sunlight exposure, he coughs up a little, just like Man of Steel.
H'El's origins are a mixture of those of Superman and Zod from Man of Steel. He is formed from countless Kryptonians over the ages, but completely, not just implanted within him as was the case with Kal-El. However, his desire for either having Krypton back or nothing at all harkens to the same film's General Dru-Zod.
No Sell: While Kryptonite can pierce H'El's skin, it doesn't sap his strength or poison him. This is because of H'El's origins.
Ret Canon: The story arc depicts Faora wearing her Man of Steel armor.
Sacrificial Planet: In order to show the threat H'El poses, Superman witnesses the destruction of an entire star system.
Save This Person, Save the World: Supergirl must prevent H'El from causing trouble during the age of the Great War, but first, Superboy must make sure she leaves Krypton in the first place.
Superboy is sent back one week before Krypton's destruction to make sure Supergirl's past self survives an attack on her life and leaves Krypton.
Supergirl is sent to Krypton's Great War to prevent the clones from dealing a heavy blow to Krypton's infrastructure.
Superman must go back and stop H'El at the exact moment of his success. He does, but leaves him in a temporal loop at the core of Krypton that prevents the planet from dying from its fate of natural causes. It doesn't seem to change the present, but for a moment, Krypton appears in the present before disappearing.
Space Station: One of these is in the orbit of Krypton and is programmed to attack enemies of the state.
Take a Third Option: During the final issue, Superman believes he can save the timeline without having to ensure Krypton's destruction, even though Jor-El says it is impossible. Also, Jor-El wants to kill H'El, but Superman instead uses H'El's unstable Time Master powers against him to trap H'El in an infinite time loop. After H'El is defeated and Superman and Supergirl return to Earth, Krypton briefly returns to life in the present before disappearing.
Teeth-Clenched Teamwork: Supergirl is less than thrilled to be working with Superboy, though it doesn't stop her actually saving his life as noted above under Beat the Curse Out of Him. She also mourns his death along with Superman upon getting the news.
Time Crash: H'El's temporal alterations cause a time tsunami, a storm that can destroy an entire star system. If the Superman family does not stop H'El, the time tsunami will destroy the Omniverse, the collection of all different universes both within and outside of The DCU.
Time Master: The Oracle opens three portals so that Superman, Superboy and Supergirl can travel to different points in Krypton's history. Meanwhile, H'El can exist in multiple timelines at once. After Jor-El weakens him with a special gas, H'El loses control of his powers and Superman traps him in an infinite time loop.