Season two of "Arrow" utilized its DC Comics source material further expand the world of Starling City, incorporating elements like "the Canary" (the show's take on Black Canary, played by Caity Lotz), Sebastian Blood, the League of Assassins, Amanda Waller and the Suicide Squad.

Yet, it's a conflict with its earliest roots in season one that has driven the main action of the season (and also taken some characters off the board to balance out all of the new additions): Main character Oliver Queen (Stephen Amell), the titular Arrow, and Slade Wilson (Manu Bennett). While the two started as allies during Oliver's time on "hellish island" Lian Yu, this season both revealed the circumstances behind Slade's quest for vengeance, and showed him fully embracing his Deathstroke persona in the present day. As the season finale, "Unthinkable," starts, Starling is under siege due to Slade's army of Mirakuru-fueled criminals, prompting Amanda Waller to send A.R.G.U.S. drones to wipe out the city to keep the threat contained.

CBR News spoke with "Arrow" executive producer Andrew Kreisberg -- who co-wrote the episode with fellow EP Marc Guggenheim, with a story by Greg Berlanti -- about topping the show's initial season finale, balancing Oliver and Slade's personal grudge with the large-scale action, the impending arrival of Nyssa al Ghul (Katrina Law) and the League of Assassins and how he views the show's evolution over the past season.

CBR News: Andrew, inherently, a season finale comes with a lot of expectations from fans for things to be suitably epic. There have already been quite a few big episodes this season of "Arrow" -- is there much internal pressure involved? Is it a priority to top what you've done before?

Andrew Kreisberg: It's definitely something we set out to do. We approached season two as a sequel to season one, in the same way as a movie sequel -- the introduction of some new characters, the sets are a little bit bigger, and the stakes are a little bit bigger. Especially in that first episode of the season, "City of Heroes," there were so many things that were done in a "sequel" way. Coming into the finale, we did feel an obligation to go big or go home, and I think that's why, in essence, the finale kind of started in episode 21, and all of episode 22 encompasses it. Whereas 22 was more of a run-and-gun episode and there wasn't as much time to stop and chat, [and] while 23 has some of our biggest, epic action scenes of all time, it also has a lot more time for reflection, and looking back on the course of the season, and Oliver's journey, and hopefully some of the more emotional scenes we've had on the show.

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It seems that the "Arrow crew" are definitely long-term planners. Is this pretty much exactly where you knew you'd end up with season two, or has there been room for improvisation along the way?

There's always room for improvisation with us. We very firmly believe in having a plan, and so many of the things that we're doing at the end of this season are not only a result of the plan that we had at the beginning of season two, but also stuff that Greg, Marc and I had discussed on the pilot. Even Sara being alive was something that we had discussed on the pilot. That was why there were so many references to Sara, and we did that storyline about Alex Kingston, playing Dinah, believing that Sara was still alive -- only to bury it, because we knew we were going to bring her back.

But the best part about having a plan is that you can change the plan. There are definitely some things in the finale that was stuff that we had thought of along the way, but so much of the structure was built from the very beginning. Especially nowadays, when people binge-watch shows, and they'll watch 10 in a row, I think there's even more of a responsibility on the writers and producers' part to not make it look like they're making it up as they go -- or if they are making it up as they go, make it not look like that. [Laughs]

As things have been ramping up leading to the finale, there's a lot going on, down to drones potentially nuking Starling City entirely, and multiple characters on the board all having a stake -- but it all stems from the very personal issue between Oliver and Slade that's been explored throughout the entire season. With so much happening, what's it like from the writing perspective to balance all of that, and do justice to the personal issue at the heart of the matter, while having this bombastic action going on at the same time?

We actually open the episode with this epic montage that recounts the sad ballad of Oliver Queen and Slade Wilson, starting with their very first meeting, up until the present, to open the show, to really remind people that everything that's happening -- whether it's the League of Assassins, or the Mirakuru army, Amanda Waller, A.R.G.U.S., the drones, the police department -- at the root is the conflict between these two men. The unquenchable anger that Slade has against Oliver, and the overriding guilt Oliver has for his culpability in Shado's death, all throughout -- especially much more than last week -- [are] these opportunities for meditations on how much of this is Oliver's fault, how much does Oliver have to keep paying, and how much will everyone else have to pay for Oliver's actions? And ultimately, can Oliver become the hero that he wants to be?

It's going to be a lot easier to talk about the finale once everyone's seen it. [Laughs] But it was definitely hard managing everything anyway. We'll leave it to the audience to decide if we got our sums right. We set up a lot of threads over the course of the season, whether it was the Suicide Squad, or Amanda, or the League of Assassins. I think sometimes those things might have seemed like left turns, but we had always planned in having this sort of epic finale where all the pieces came together. Hopefully we pulled it off.

You mentioned the League of Assassins, and one of the things confirmed happening in this episode is the return of Nyssa al Ghul. But she's not by herself, right? We're going to see the League en masse?

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Yes. You will discover early on that is where Sara went during her brief sojourn, when she said, "I'm going to see a friend." She was talking about Nyssa. As somebody says in the finale, when you're facing an army, you need an army to fight back -- and now Oliver has it.

Another pivotal character over the last few episodes is Laurel, who has definitely become more involved in the central action than she had been, especially now that she knows Oliver's secret. I've heard you speak before about how much that opens things up, but now that the character has passed that threshold, how much in your opinion has that expanded her potential even further going forward?

For us, it's huge. We've found that the minute anyone knows about Oliver's secret, they become far more fun and easier to write. We've had varying degrees of success moving Laurel's character through season one and season two -- I know not everyone has always been on board with the journey that she's taking, but we felt that whatever choices we made, it was all in service of leading up to this finale. I think people are going to be happy to see where she's going.

With the season wrapping, and building the world of "Arrow" much bigger than it was, what are some of the things that stick out to you as the proudest elements of what the show has been able to achieve this time around?

I think the show has gotten a lot more emotional. Full credit to our amazing production team, and our producers J.P. Finn and Todd Pittson, our stunt coordinators, our directors and our DPs, for making the show look bigger and bolder. I know a lot of people said throughout the season, "Oh, wow -- they have so much more money, and it shows." And the truth is, we didn't have more money -- we actually had less money. That, I don't take any credit for.

But those quiet moments, like when Sara first showed up, and her father saw her alive -- there are so many things that we saw this season that even as a producer, even though I had seen them a bunch of times, I would still get misty and still got emotional. There's one thing in particular in the finale that I get misty-eyed every time I watch it. We always had high hopes for the show. We always looked at season two en masse as a sequel to season one, and like any good sequel, it goes deeper emotionally, and really gets underneath the characters. That's the thing that I really take away from this season. Everything went up a notch.

The "Arrow" second season finale, "Unthinkable," airs 8 p.m. Wednesday, May 14 on The CW.