Katie McGrath Says the Legion of Super-Heroes is a "Massive" Part of 'Supergirl' Season 3

, and so the question for McGrath became: will Lena Luthor deal with the Legion?'It's such a [...]

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During an interview last week on the set of Supergirl, Katie McGrath (who plays Lena Luthor on the CW hit) said that the Legion of Super-Heroes would play a "massive" role in the show's third season.

It is expected that the Legion will be introduced in next week's episode, "Wake Up," which brings back Mon-El (Chris Wood), a character who disappeared at the end of the show's second season. A brief glimpse of what appeared to be the interior of a Legion ship on a recent episode, coupled with longtime fan assumptions that the introduction of Mon-El (known by several names in the comics, but most often Valor) would lead to the introduction of the Legion. The recent casting of Saturn Girl and Brainiac-5 seemingly confirmed the long-assumed idea (series star Melissa Benoist asked reporters at a press event last week whether anyone was really surprised by it), and so the question for McGrath became: will Lena Luthor deal with the Legion?

"It's such a massive part of a season 3, I would imagine that yes, she will be," McGrath answered. "We've only just gotten the scripts where they come in so we don't quite know how they're going to interact with all of the characters because they've only just arrived. But I can't imagine that it's not going to have an effect on her. For a start, Kara is her best friend and the love of Kara's life has just come back. So that is going to impact on everyone, I think."

The Legion of Super-Heroes are a team of teen-aged superheroes from the future, all of whom wear "flight rings" like one previously seen onscreen at Superman's Fortress of Solitude. Both Supergirl and Mon-El have long histories with the group in the comics.

The Legion has previously appeared on TV in the Superboy and the Legion of Super-Heroes animated series as well as in an episode of Smallville titled "Legion."

Following an absence that defined much of the first third of Supergirl's third season, Mon-El will reappear next episode, but he will apparently not be himself -- and if the "tubes" on board the Legion ship are any indication, he will also not be alone.

Supergirl airs on Monday nights at 8 p.m. ET/PT on The CW.