The Death of Superboy

The Legion of Super-heroes was an unforeseen casualty of Crisis on Infinite Earths.

The Legion hadn't just been a spin-off of Superboy, they eventually took over his series.  A few years before the Crisis, Superboy had retired from the Legion to spend time with the Kents back in Smallville before their deaths.  The Legion continued in their own series in the 30th century without him, and aside from acknowledging the death of Supergirl during the Crisis (but strangely not in an actual Crisis tie-in), it had mostly ceased to be a Superman-related property.  It was unusual that the Legion's continuity remained wholly intact after the Crisis, since its inspirational figure, Superman, had not.  So when post-Crisis Superman had no longer been Superboy as a teenager, it forced DC to have to devise a new origin for one of their most popular superhero teams.  This would be the first of several attempted fixes to their continuity over the next 20 years, but like most of the subsequent attempts, it would create more confusion than it resolved.

Legion of Super-Heroes #37

After an attack by the villainous Time Trapper, a team of Legionnaires led by Braniac 5 takes a new and improved time bubble into the time stream to try to reach the Time Trapper at the end of time.  Instead, they end up in the past in the town of Smallville where they first met Superboy.  Half the team guards the time bubble while the others (who can blend in) go into town to find their friend.  Superboy, however, turns on his former teammates and uses a projector device to freeze them in time stasis.  He attacks the others but they escape into the time stream and Superboy follows them, while the Time Trapper watches everything unfold from his vantage point at the end of time.

It's clear the Legion is exploring their own pre-Crisis past; Pete Ross is still an honorary member and knows Clark Kent's secret identity, while Lana Lang does not.  Throughout this story, the Crisis is referred to as the "red skies."

Superman #8

The time-lost Legionnaires end up in the present day Smallville, where they encounter the post-Crisis Superman who has no memory of them.  After a skirmish, Braniac 5 tells Superman about the Legion's history and the recent events that brought them there.  Superboy ambushes them and freezes them all with his ray.

Half of this issue is spent in flashback.  It seems odd that it goes into so much detail over pre-Crisis history that wouldn't be referenced again after this story.  The recap from the previous issue literally repeats the same pages from that book, apparently just with different inking. 

Action Comics #591

Superboy flies off with the frozen Legionnaires and leaves the Man of Steel, where the stasis effect wears off.  Superman catches up to Superboy as he escapes with the time bubble, following them through the time stream where he crashes into Superboy's Smallville.  Meanwhile in space, Superboy's pet dog Krypto senses trouble on Earth and flies back to help his master.  Watching events unfold at the end of time, the Time Trapper gives the reader a convenient expository monologue about how he created a pocket universe and populated it with a Superboy.  Each time the Legion thought they were traveling to their own past, the Time Trapper was really sending them this universe.  While Superman and Superboy fight in the air, Krypto goes to Superboy's lab in the Kent's basement to fetch some kryptonite.  Krypto sadly exposes himself to Gold kryptonite and permanently loses his powers and his intelligence, becoming an ordinary dog.  Pa Kent tries to stop Superman with the kryptonite, but it has no effect on him (just as pre-Crisis Superman was unaffected by kryptonite from other Earths).  Superman deduces that Superboy was trying to lose the fight all along and now that they're all on the same team again, the Legion takes Superman back to his 1987 Metropolis and Superboy and the Legion go on to confront the Time Trapper.

This send off would be the last we would see of these pre-Crisis versions of Superman's supporting cast.  While most post-Crisis Superman stories have tried to be modern in approach, this one relishes in its old-fashioned elements, like the flashbacks and Krypto's thought balloons.  The differences between pre and post-Crisis Superman would probably never be more visible.

Legion of Super-Heroes #38 

Superboy and the Legion go back to Superboy's Smallville for the final confrontation with the Time Trapper at Smallville High.  The Time Trapper offers to save this universe if Superboy will kill the Legionnaires.  Superboy chooses to fight instead, but in the process accidentally smashes the device that was still keeping the pocket universe intact.  Superboy channels the machine's energy through himself and somehow saves his world, although it's not really explained how.  Unfortunately, the energy is killing him, but before he dies he brings the Legion back to their own time, as he seems to be the only one who could willfully pass through the Time Trapper's barrier.  Superboy dies in Mon El's arms and the Legion mourns.

The death of Superboy was a plot device designed simply to write Superboy out of continuity.  Despite the Legion's words of admiration at his funeral, he wouldn't be mentioned in the series again after this.  The explanation of the pocket universe was overly-complicated, but the reality is it was never intended to be a serious point of continuity.  The explanation is barely within the lines of the post-Crisis rules of no parallel earths and no other Kryptonians.  While a lot of what happens doesn't make much sense, the only things you really need to know are that Superboy is gone and the Legion can no longer time travel.

In a few years, the Legion would further re-invent itself with a soft reboot "5 years later."  At the tenth anniversary of Crisis on Infinite Earths, the Legion would finally get a hard reboot, starting over with no connection whatsoever to Superman this time.  There would be more cancellations and more reboots, but the Legion would never be as popular again as their pre-Crisis version.

Adventures of Superman #431

Adventures of Superman sits out the Legion crossover.  Superman fights an uninspired new villain, Doctor Stratos, who uses a satellite to control the weather.  Stratos seriously believes he's a Greek god and just is using technology as a substitute until his godly powers manifest.  He disappears after Superman defeats him, but on the last page he seems to have actually developed real powers from a lightning strike and vows to use them to destroy Superman.  As far as I can tell, though, this is his one and only appearance.