As "Supergirl" reaches its season finale, the stakes have never been higher on the CBS drama.

With National City and her sister Alex under the influence of the Myriad project, Kara (Melissa Benoist) must discover a way not only to free them all but also defeat Non (Chris Vance) and Indigo (Laura Vandervoort). If Supergirl fails, surely Earth is doomed.

Ahead of tonight's finale, "Better Angels," Vance spoke with CBR News about creating a three-dimensional villain, underestimating Supergirl, and Non's dynamic with Indigo.

CBR News: How did you become involved in "Supergirl"? Did you go through a secretive audition process?

Chris Vance: It was very secretive. It was between myself and [executive producer] Andrew Kreisberg, and that was it. We sat down and we had a conversation. He showed me some of the material he was working on and the early stuff they were producing that season. I was like, "I'm in. C'mon. What can I do? Get me in there." Andrew was kind enough to give me the part.

How much did you look at other iterations of Non?

It's the first season of the show, so the producers have their vision -- a spectacular vision, in my opinion. I wanted to fulfil that as an artist. I talked to them endlessly about their interpretation of Non and how best I could get near it. I was guided by their vision. As an actor, it was a challenge to fulfil their vision. I gave it a good shot.

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Most viewers recognize the name Non from "Superman II," where he was more brawn than brains. It seems "Supergirl's" Non is a balance of both qualities.

I tried. Sometimes in television, because it's not a snapshot in time, as a performer you have to provide a little more access into a character for the audience. There is obviously a character arc and a journey. We concentrated on the human side of Non, who is in mourning of Astra [Laura Benanti] and wants to fulfil her destiny, her vision, through Myriad. Of course, he still has that angry military compulsion, but I tried to make him human in some sense.

Astra developed the mind-controlling Myriad to prevent Krypton's destruction. Non gave this speech about bringing peace to Earth and saving mankind. Do you feel he actually has the planet's best intentions in mind, or is he a power-hungry tyrant?

I tried to play the first one, because it's very easy to go the power-hungry tyrant. That's pretty one-dimensional. If you think about it, it's a very interesting question given where we are as a species. We are something of an infestation as a species. If there weren't 7 billion of us, what would be happening? I tried to play the conviction that Non means what he is saying. If he gets rid of the human race, he's saving a planet.

At the same time, Non's partner in crime, Indigo, pushes his buttons. How would you describe their dynamic, and who exactly is using who?

That's a very good question. Undoubtedly, Indigo is using Non. Is he using her? Yeah, I'd say so. Layering in the underlying sexual tension after Astra's departure is another interesting development. Maybe they are both using each other in that sense for comfort. I don't know. It was certainly in the writing, so we played it. Why not?

What can viewers expect from the climatic showdown between Supergirl and Non in tonight's finale?

Without giving the old "spoiler alert," they really ramped up the writing at the end of the season. All I can say is Supergirl really gets forced into a difficult situation. She literally has to save every human being on the planet or fail miserably. They really ramped it up. Poor old Melissa [Benoist] was running around like crazy because she's in everything and has to be the savior. Is she or isn't she at the end of the episode? I can't tell you.

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Non comes off stronger and more ruthless than Supergirl, so does he underestimate her?

Yes, he does. Secondly, I tried to play out an underlying, almost love, for Kara Zor-El with a history of family, which is obviously very important to Kryptonians. I tried to find Non's compassion, his human side, and may be a little bit of admiration for his niece. Otherwise, it becomes one-dimensional and it's not so easy to play out. Does he let his emotions get the better of him and put her under several tasks that are really unfair? Yeah, sure, but you need some underlying humanity to him, so it doesn't become boring to play and boring to watch.

With "Prison Break" and the "Transporter" TV series under your belt, you're no stranger to action. In what ways did "Supergirl" allow you to expand your stunt repertoire?

I've done most of it before. The only thing with this one was playing the superhero, you have up-in-the-air wire gags and trying to ballet dance, run dialogue and do the action sequences while hanging off wires, all against green screen. It was terrific fun and a challenge.

Astra had a soft spot for Kara. Indigo wants to wipe out the human race. What are your thoughts on Non having a change of heart on his current path?

His biggest thrust is to fulfill Astra's vision. He's like a dog with a bone with that one, so he won't let it go. While he might want other things and second guess himself, I don't think he's every going to let the vision drop, not until his last breath.

Over your career, you've fallen on both sides of the law. What's been fun about playing someone as powerful as Non?

It's a challenge to represent a superhero or Kryptonian villain and embrace that strength. It's a challenge physically. Then, to play this character two or three-dimensional, instead of one-dimensional in this genre, I had to find every conceivable nuance that I could put into Non in terms of his humanity and compassion. I keep going back to that, but the important quality is his humanity, even though he's Kryptonian.

The season finale of "Supergirl" airs tonight at 8 ET/PT on CBS.