'Supergirl': Could the Legion's Real Mission Be to Stop Crisis on Infinite Earths?

Supergirl is currently on hiatus while Legends of Tomorrow wraps up their third season, but while the Girl of Steel isn't on television she's still on the minds of fans, specifically when it comes to what the Legion of Super-Heroes' real mission might be.

At the end of the last episode of Supergirl before hiatus, the Legion is on a secret mission, one that not even Mon-El (Chris Wood) knew the true nature of. While there has been a lot of speculation as to what the team's real mission is -- including that the Legion is there to save Supergirl from Reign -- there's another theory, one that has major implications for the rest of the Arrowverse. Could the Legion's real mission be to prevent Crisis on Infinite Earths?

For those who aren't familiar, Crisis on Infinite Earths is a landmark DC Comics event that served to end the multiverse concept within the DC Universe and depicted the deaths of major DC characters Supergirl and Barry Allen's Flash. While the story is fairly complex -- it spanned 12 issues of an eponymous limited series and had a number of tie-in books as well -- the nuts and bolts are that the evil counterpart to the cosmic being the Monitor, known as the Anti-Monitor, begins destroying realities with a wave of antimatter as he is bent on becoming the one ruler for all reality.

To stop Anti-Monitor, Monitor recruits heroes from across all time and space to set up five towers where they will merge the various worlds of the multiverse into one in order to make it stronger. Unfortunately, Monitor is murdered by his assistant Harbinger/Lyla Michaels who has been possessed by Anti-Monitor. The death ends up sending the last five Earths into a protective state of limbo, but that turns into a war when Anti-Monitor tries to manipulate some of the Earths against the others. Harbinger -- who reverted to her normal self after the horror of what she had done -- then recruits the heroes of the remaining Earths to fight back. The heroes are eventually triumphant over Anti-Monitor, but not without a cost. Supergirl and The Flash are both killed while the five remaining Earths merge as one, resetting the universe and history as we know it.

In comics, the Legion doesn't really have much of a role in Crisis on Infinite Earths. In fact, the event ends up with the original Legion team being split into two distinct alternative timelines, creating a continuity mess for several years in terms of publication with another team whose stories diverge from this point popping up in books later on — the Legion's complex history could be a story of its own.

However, the Arrowverse is far from a literal adaptation of the comics and as a result it's possible that, being from the 31st century, the Legion may know of something that happens in the present that has dire implications. One of the things that has already been mentioned on Supergirl is that an extinction-level event occurs sometime in the future and wipes out most of the historical record. It's possible that the event they're referring to is actually the merging of the multiverse in Crisis. Even in comics, when the various Earths merged some people were completely erased from existence as the worlds replaced one another. That kind of event could account for the lack of history or records from that time as, technically, time didn't exist before then. It might also explain that, according to the Legion, Reign simply leaves at some point. Maybe she didn't so much leave as cease to exist.

This could also explain the appearance of the Mystery Girl on The Flash. Appearing during the Supergirl hour of this year's "Crisis on Earth-X" crossover, many have speculated that she's either Barry and Iris' daughter or granddaughter from the future. While either of those could be true, what purpose would she have to come to the present -- and on Earth-1, no less -- if there wasn't a reason for it? If the Mystery Girl is Dawn Allen or Jenni Ognats and a member of the Legion, she may be stationed on Earth-1 away from the rest of the team in an effort to help prevent the looming Crisis.

Even if the Legion is on present day Earth-38 to prevent a Crisis on Infinite Earths type event, they have a more pressing threat to deal with as well. The Worldkiller Reign is proving impossible to defeat for Supergirl and now that there are more Worldkillers out there to help her, if they don't manage to stop Reign, there may not an Earth-38 to save from a merging of the multiverse.

Supergirl airs on Monday nights at 8 p.m. ET/PT on The CW. New episodes resume on April 16th.