5 Essential Legion of Super-Heroes Stories to Read After Tonight's 'Supergirl'

The Legion of Super-Heroes made their big debut on Supergirl tonight, stepping up to help fight against the rise of the Worldkiller, Reign.

For fans, tonight's appearance of the team finally makes good on the various hints and teases of the team The CW series has made during its first two seasons, including a prominently displayed Legion flight ring in Superman's Fortress of Solitude and Interlac graffiti on the walls of the alien bar. But now that the Legion is here -- and looks like they might be sticking around for a while -- here are some essential reading to help you better understand who the Legion of Super-Heroes are and some of the many adventures the classic DC Comics team has had.

'Adventure Comics' #247

When it comes to the Legion of Super-Heroes you would be well-served to start at the beginning. Not only is Adventure Comics #247 a fun read, the 1958 issue also marks the very first appearance of the Legion of Super-Heroes. In the issue, Superboy, a young Clark Kent, is identified by two other young people as Superboy, and later a girl outs Superboy as Clark Kent. It turns out that the three teens are the Legion of Super-Heroes, a team from the 30th century. Identifying themselves as Cosmic Boy, Lightning Boy, and Saturn Girl, the team has come back to the 20th century to offer Superboy membership in the Legion.

They all head off to the 30th century where Superboy goes through initiation in which he must complete certain tasks before the Legion can beat him to it. Superboy fails each time and is initially upset, but it's revealed that the whole thing was rigged. The Legion already decided he could join. Now a full member of the Legion of Super-Heroes, Superboy heads back to the 20th century, complete with a medal he shows off to his parents.

"The Great Darkness Saga"

Published in 1982, the five-issue "The Great Darkness Saga" story arc might just be the most complete representation of Legionnaires up to that point in time as the series features appearances of nearly every living past and present member, not to mention almost all their 30th century allies as well -- including the team made up of Legionnaire rejects, the Legion of Substitute Heroes. Yes, they're a thing.

In the story arc, the Legionnaires find themselves dealing with attacks by beings of great power who call themselves servants of a master of Great Darkness. The Legionnaires quickly discover that this master is serious as even the Time Trapper -- himself a huge Legion foe -- has had his abilities drained by the mysterious threat. They also discover that the "servants" are actually "reverse-DNA" clones of powerful heroes, such as Superman and even the ancestor of one of their own.

Saidmaster turns out to be Darkseid. The Legionnaires successfully fight him, with the defeated Darkseid literally packing up Apokolips and taking it with him, but as he leaves he declares that he's left them with a "curse of darkness" that will destroy them. Months later, the pregnant Saturn Girl gives birth to her child with Lightning Lad, but during delivery everything is mysteriously covered by darkness before a single, healthy baby boy is born. Saturn Girl is surprised by the single birth as she had thought she sensed two babies during her pregnancy. As it turns out she was right; Darkseid kidnapped the second child, transformed it, and sent him deep into the past to encounter the Legion as the villain Validus, thus fulfilling his own curse.

"End of an Era"

A tie-in to the Zero Hour: Crisis in Time miniseries, "End of an Era" is the final story arc of the original Legion of Super-Heroes timeline, thus serving as the end of an unbroken 36-year continuity for the team. In the arc, two of the Legion's greatest enemies, Mordru and Glorith, unite, the Time Trapper shows up, and timelines and universe are literally unraveling around the heroes. With time completely jacked up, the adult legion must reunite with their younger versions, realign time, and save literally everything. The arc ends with a couple of surprises. First, the Time Trapper reveals that his actual motivation for things was an attempt to save the 30th century from an impending time cataclysm, but that his plan to save things drove him mad -- leading to a timeline out of whack. The second is that the Legionnaires sacrifice themselves, joining hands as all reality disappears into a white void.

Following "End of an Era", the Legion underwent a complete reboot though Infinite Crisis restores much of the original Legion continuity later. It's a wild story arc, but one worth reading -- especially with the Legion now part of the Arrowverse and time-related matters getting extra weird on Legends of Tomorrow.

"Legion Lost"

As the title suggests, this story sees the Legion -- Saturn Girl, Brainiac 5.1, Chameleon, Umbra, Kid Quantum, Live Wire, Apparition, and Monstress -- lost on the far side of the universe and looking for a way home. While this is going on, they also discover an alien race known as The Progeny who are carrying out a horrific genocide on the galaxy. There is also internal stress that the Legion must deal with. Umbra is struggling with having been possessed by The Blight, Monstress is having issues with the "no killing" rule as she wants to end the Progeny, and Ultra Boy is having a major case of separation anxiety. Things take a turn for the worse when it's revealed that Saturn Girl had been using her telepathic powers to manipulate everyone, going so far as to have created a psychic illusion of Apparition who was not really there with them.

Things come to a head when the team discovers that their missing teammate Element Lad has gone insane and is now the supreme leader of the Progeny. Without giving too much away, the ending is of "Legion Lost" is at the same time both satisfying and difficult, with the team managing to return home, but not without some major changes. It also serves as a great re-introduction to the team.

"The Lightning Saga"

Serving as the reintroduction of the Legion in a post-Infinite Crisis landscape, "The Lightning Saga" sees the Legion restored one at a time by the JSA and the JLA as they discover that the Legionnaires have been displaced in time, and none of them are in a good place. A villain named Trident turns out to be Karate Kid, Dream Girl is being manipulated by Doctor Destiny, Wildfire is frozen among statues of Legion members and so on. However, as the discovery of the Legionnaires continues, Superman realizes that the team is planning "Russian Roulette", something they had done before to restore Lightning Lad to life.

The JSA and JLA are unable to stop the Russian Roulette. Karate Kid is struck by lightning, but survives. Wally West and his family return while the Legion goes back to the future -- where it's revealed that the team did come back with someone, and they're trapped inside Karate Kid's lightning rod.

Supergirl airs Mondays at 8/7c on The CW.