[Warning: The following contains spoilers for Thursday's episode of DC's Legends of Tomorrow. Read at your own risk!]

DC's Legends of Tomorrow are back in action — literally, considering everything that happened in the sophomore season's second episode, "Justice Society of America."

By the end of of the hour, Rex Tyler (Patrick J. Adams) was erased from the timeline by Eobard Thawne (Matt Letscher). Nate (Nick Zano) got a dose of super powers, Professor Stein (Victor Garber) sang, Sara (Caity Lotz) took over as captain of the Waverider and, oh yeah, we got a full introduction to the Justice Society of America.

Executive producer Marc Guggenheim helped break down the episode and what we can expect next on Legends of Tomorrow after an episode screening event. Check out what he had to say below.

Patrick J. Adams, <em>Legends of Tomorrow</em>Patrick J. Adams, Legends of Tomorrow

Hourman is erased in the timeline this episode. When you first introduced Rex Tyler did you always know you were going to get rid of him this way?

Marc Guggenheim: When we introduced Hourman we actually had a whole bunch of different potential scenarios. That's one of the things about a time travel show, you almost have to go through more permutations of the story than even is normal because of the time travel element. That was always one of the notions. One of the things we talked a lot about was, at what point do we show the audience the moments just after [episode] 116? We had a version of [the Season 2 premiere] that actually had the flashback you saw in [this episode]. We decided to move it into [this episode] and shoot it as part of [this episode]. We talked a lot about just how we were going to reveal the information, all the different ways we could deal with the ramifications of [episode] 116. We had a lot of different notions that were fighting their way to prominence in the writer's room. This is the one we went with.

How are you going to keep the Justice Society in future episodes? The Legends can't just keep going back to 1942.

Guggenheim: You're absolutely correct. I don't want to spoil too much. I will say that we do go back to 1987 and we'll meet a much older version of Obsidian, who is going to be played by Lance Henriksen. That's one way. We have another device up our sleeves that I don't want to spoil because it deals with stuff that is mythology-based in the back half of the year.

We do know that Vixen is going to be sticking around. Is there anything you can say about how that is going to come to be based on how this episode ends?

Guggenheim: We'll deal with it very directly in [the next episode]. We actually pick up facing that issue head on. I think you have a clue to it in Rex's final words to her. If you're Vixen and you've got Rex Tyler dying in your arms and you hear the words "time traveller," who would you think is responsible?

Legends of Tomorrow: Everything you need to know about Season 2

Will the team take up a more active role in trying to find Rip? They seem sort of like, "Oh, hopefully we'll bump into him at some point."

Guggenheim: That's something that's always going to be going on in the background, and sometimes in the foreground of various episodes. [First of all], we don't want change the mission statement of fixing aberrations to going and saving Rip. The bat has kind of been taken out of their hands in the sense that there's no way to find Rip. What would they do? Even if they said, "Okay, this is priority No. 1, finding Rip," I don't know how they'd go about it, given the nature of Rip's disappearance.

You make it sound like we might not see Rip for a while, either. Are we going to know before the Legends do [where is he is]?

Guggenheim: You will find out before the Legends do.

The CW DC Universe crossover gets their big bad

Can you talk about Nate's powers now? He's obviously getting them at the end of this episode, but can you talk about how unpredictable they might be because it seems like it was a little bit of a rough job for Ray to create this.

Guggenheim: One of the reasons we wanted to bring the character Nate into the show was we wanted to play with something that Flash really got a chance to play with in Season 1, which is the fun of telling an origin story for a hero. In the evolution of a hero, there are all these fun seminal moments that we wanted to put our own Legends spin on. Part of that is discovering you have powers. Part of it is learning how to control those powers. Part of it is the first time you go out in costume, the first time you fail, the first time you realize you have a weakness. We wanted to be able to tell all those different kinds of stories. You can safely assume that the reason we brought in Nate was so that we could tell those kinds of stories, including the unpredictable nature of his powers. The next episode really shows how difficult it is for Nate to get his powers under control.

Legion of Doom was announced at San Diego Comic-Con on Legends. Is there there anything you can say about how the other two members might come in and when they might come in?

Guggenheim: We're going to see Malcolm Merlyn [John Barrowman] in episode 208, which is our mid-season finale.

Legends of Tomorrow to introduce the Legion of Doom in Season 2

Can you talk more about Sara taking this leadership role on?

Guggenheim: It's funny. Sometimes you come up with character journeys for the season and sometimes they work out better than you ever expected. There's other times when it's worse than you ever expected. I have to give a lot of props to Caity Lotz. As you start to see her become more and more comfortable with becoming the leader of this rag tag group, it's so much fun to watch her. The character is embodying the role of a leader. Caity's performance really embraces it. I think it turns out to be one of the most successful things that we've done in Season 2. I'm super excited about.

Thank you for reminding us that Victor Garber is a Broadway star.

Guggenheim: The way that came about was, we had Greg in and we were pitching him the Legends infiltrate this cabaret in Nazi occupied Paris and he's like, "Well, you've got to have Victor sing." I jokingly shot back to him, "Like, what? He sings Edelweiss?" He's like, "Yes, do that!" and that's what we ended up doing. We love Victor. We love it when he sings.

What was some of the fun of designing the JSA headquarters? I noticed a few of the Easter Eggs you stuck in there?

Guggenheim: I pulled a lot of comic book references for the art department. I really, really wanted it to have that brown stone look, chock full of trophies, with, for sure, at the top of my list was a table with the Justice Society emblem on it. As far as the different Easter eggs, those were actually all the brain children of the art department and the set dressers. Sometimes I will specifically call out, "Oh, I'd really like to see x, y and z in there," but I didn't do that in this case. I think they crushed it. I think they did an amazing, amazing job. That was a real location that we brought in set dressing for. We didn't build that as a set.

CW's superhero producers tease four-show crossover, coming out storyline

What about the costumes for the JSA? What was that process like?

Guggenheim: This was obviously at the beginning of the season and Maya Mani, who is our superhero costume designer across Flash, Arrow and Legends, was busy building all the new suits, not just for Legends but for Flash and Arrow as well. Vicky Mulholland, our costume designer on Legends, she took the lead on Dr. Mid-Nite, Obsidian and Star Girl. That was new for us. We felt a certain amount of leeway. It also depends on the costume. I think that Star Girl's costume is so iconic and so easily adaptable. It's a different kind of costume than say Dr. Mid-Nite or Obsidian, where you may need to take a bit more license to translate it to live action. There's some costumes that are just like, "Oh, bam. That's just pre-a-porter," like Wild Dog [on Arrow]. Then there are other costumes that take more work and it depends totally on the nature of design.

DC's Legends of Tomorrow airs Thursdays at 8/7c on the CW.

(Full disclosure: TVGuide.com is owned by CBS, one of the CW's parent companies)