“They will call you Worldkiller…”

But why? And what does that even mean? If you’ve been following The CW’s Supergirl this season and aren’t particularly well versed in Kara’s comic book history, you might have found yourself asking those questions two weeks ago after finishing “Wake Up,” which ended with Odette Annable’s Samantha seemingly awakening some dark Kryptonian power within her.

Compared to some of the villains that Kara has faced, like Metallo, Parasite and Mister Mxyzptlk, Reign isn’t widely known. But the comic book version of her has a fascinating backstory which is closely tied to that of Kara and her fellow Kryptonians.

Reign is a relatively new addition to the DC Universe, having made her first appearance in early 2012 in The New 52’s SUPERGIRL #5. Supergirl, like all DC comic books, went through a relaunch in 2011 and Supergirl’s creative team at that time, writers Michael Green and Mike Johnson and artist Mahmud Asrar, chose to create new villains for their first two storylines. Reign was the second they introduced and the first that wasn’t human.

After Kara awoke on Earth, the sunstone that was in her pod led her into space and to an abandoned Argo City—the only remaining remnant of Krypton. While there, she learned the truth about her home world and the death of her parents before finding herself confronted by Reign.

As you can likely deduce, Reign wasn’t Kryptonian, but she was a product of Krypton. She was what they called a “Worldkiller,” a mysterious and feared weapon built far off-world by Kryptonian scientists that was eventually deemed too terrible and destructive for actual use. Placed in stasis and never brought down to Krypton, Reign awoke with no real memory of her life prior to awakening. She came to Argo City and eventually Earth searching for answers about her past.

She also wasn’t alone. There were five Worldkillers in total—each of a different alien race and possessing a different skillset. Of the five, Reign’s powers were the most like Kara’s. She had super strength, invulnerability and the power to fly, plus was an excellent tactician. Her fellow Worldkillers could manipulate energy, generate viruses and toxins and uproot terrain, and it was only by using their abilities against each other that Kara was able to defeat them.

Though it’s highly debatable whether Kara really did defeat them. For a villain who has only made one three-issue appearance in the DC Universe, Reign has a surprising amount of depth. She’s thoughtful and in many ways sympathetic towards Kara. In fact, initially Reign didn’t seek conflict with Kara, but comradeship. The Worldkillers were genetically manipulated and altered to become powerful weapons with an unwavering urge to conquer and destroy. But none of the Worldkillers knew where they were from, and together they sought their home worlds as they looked for answers about what had happened…much like Kara found herself doing in her earliest days on Earth.

Sensing this common ground between them, Reign thought that the Worldkillers and Kara could seek the answers they both wanted together. Of course, Reign also thought that before they did that, they could get to know each other a bit better by conquering Earth together, so yeah, there was never going to be an alliance between them.

This drive to take the planet they’d found themselves on eventually consumed Reign and Supergirl found herself battling four of the Worldkillers at once (the fifth wasn’t revealed until much later in the series). Under the command of Reign, the team of weapons ultimately retreated from the battle and left Earth after Supergirl succeeded in poisoning one of them. While Reign claimed it was because she couldn’t afford to lose a single one of her companions if she wanted to carry out her plans, it seems just as likely she had come to respect the Girl of Steel enough that she didn’t want to see her defeated. And this makes sense. After all, the two of them had found themselves at odds simply as a result of the Worldkillers’ programming. You take out that one small, inconvenient detail and Supergirl and Reign have far more in common than they do that’s different.

Which brings us to the Supergirl TV show. While so far we’ve only been given a few details on the show about who Reign is, why she’s on Earth and what she’s supposed to accomplish there, we’ve heard her called “Worldkiller” several times. She also wasn’t initially introduced as an adversary, but a friend. Kara’s built up a relationship with Samantha over this season and you have to wonder if that might impact her relationship with Reign now that she—whatever form she may take on the show—seems to be in control.

Unlike in the comics, this version of Reign seems to have been sent to Earth as a child, much like Kara. She was also raised by human parents, only Samantha didn’t know she wasn’t human or possessed powers until just recently. And in the most intriguing difference of all, Samantha has a daughter. What is all of this going to mean for young Ruby? And is it possible that she might have super powers as well?

However, it’s the possible similarities to the comic storyline that will probably be of most interest to longtime fans. While it seems pretty likely that Reign’s mission will be to conquer or destroy Earth—she is still called Worldkiller, after all—we don’t know if her reasoning will be as simple as it was in the comics, or if there will be any other Worldkillers. Samantha seems to be Kryptonian rather than some other alien race, so if there are other Worldkillers, they may appear human as well. Perhaps there are others who will be awakening over the episodes ahead?

I don’t want to speculate too much. Tonight’s episode promises to fill in several of the blanks when it comes to the show’s version of Reign, and perhaps we’ll all know a lot more when Supergirl heads into her hiatus. In the meantime, if you’d like to read the Reign comic storyline, it can all be found in SUPERGIRL VOL. 1: LAST DAUGHTER OF KRYPTON. Or just relax and enjoy the show’s version of the story as it unspools on Supergirl. Either way, we suspect you’ll agree with us when we say that when it comes to this underseen baddie, we’re hoping for a long and exciting Reign.

Supergirl's midseason finale, "Reign," airs tonight at 8 p.m. (7 p.m. CST) on The CW.