Leonardo "Leo" Da Vinci's (Tom Riley) time has come to an end. After three seasons of adventures, secrets, womanizing and inventions, "Da Vinci's Demons" has been cancelled. But, there's a full season left to be aired on Starz, and Riley and showrunner David S. Goyer promise the show is going out with a bang and not a whimper. Not only does Italy find itself under siege from the Turks, but Leo must finally contend with the ghosts from his past.

Ahead of tonight's season three premiere, "Semper Infidelis" -- and with the complete third season now available to Starz subscribers via Starz On Demand and online on Starz Play -- Riley and Goyer spoke to SPINOFF about invading Turkish forces, giving closure to the characters and the fabled Book of Leaves. Additionally, Riley shared his answer of which Marvel superhero is on his bucket list to play.

SPINOFF ONLINE: David, a busy schedule has kept you from being a showrunner this season. How hands on have you been?

David S. Goyer: A lot more than I intended to be in the beginning. I came back in during production, and then during post-production I was in every day by the end of it. Then I ended up directing second unit when we went back and did digital photography and writing some of the scenes as well. John Shiban did a great job, but I realized it was harder to step away than I thought.

Every series experiences growing pains. Looking back, what went right or wrong with this show for you?

Goyer: There were tremendous growing pains the first season. It was a very difficult show to make. It was ambitious. It didn't really look like any show that had been done. There were a lot of virtual sets, a lot of set extensions. But, a lot of things we did out of the gate right. The casting was pretty much flawless. Most of the challenges had to do with creating a studio from scratch. It was a much bigger production than most of the crews in Britain had ever encountered in a television show before. It was a much more complicated show in terms of post-production than any of us had anticipated. By the second and third seasons, that had all settled down. That always happens when you're starting a new show, particularly a show that doesn't fit into an easy niche. It's not like, "OK, this is an FBI show. I know what we're doing." It was a graphic novel version of a historical world.

Tom, season two ended with a bombshell. Leo found his mother and was about to blow her up. Where do things pick up?

Tom Riley: We pick up a few minutes previously to that. We take a little reverse in time and see what was happening just prior to that discovery. Then, we pick up immediately. The decision that Leo makes as a result of seeing his mother on that ship is the thing that causes every action in the final season. It ripple effects from that decision onward.

The Turks are a major threat. How will their invading forces push Leo and his Scooby Gang to the limits?

Goyer: We always knew Season 3 was going to revolve around the siege of Otranto, which is when the Ottoman Empire invaded Southern Italy. Season 3 is a bit different than any other season in that it takes place in a much more compressed timeline. That siege gave us a natural structure, but we didn't know going into this season that it would be our last. That kind of helped as we were finishing up. I pulled some things forward that would have happened at the end of later seasons.

Riley: For the last two years of the show, Leo hasn't really had to deal with any of the consequences from his actions. He's been very laissez-faire with his attitude towards his inventions of destruction. If there's been collateral damage, so be it. He's moved on. Technology has moved on. He hasn't thought too hard about what he's caused. This time around, it's far more dangerous. What he realizes is that he and all of his friends have been all pushed to such an extent that he's going to lose some of them.

The teaser trailer promises characters will rise and fall. What are some of the hard choices Leo has to make and how do they impact him?

Riley: The hardest choice we see almost immediately. From that point onwards, he is torn between staying behind and helping to save Italy and helping to rectify the mistakes he's made, or abandoning it and working for the enemy. He may realize in this season that actually that's the same thing. In order to rectify certain mistakes, he will have to work with those people responsible for all his actions in the past. He's going to have to side with people who have been his nemeses up to this point.

Leo discovers the Turks have fully realized his weapon designs. How does that throw him for a loop?

Riley: Well, completely, and not just that they've realized them, but that they've made them better. Somehow, they have taken his designs, that he thought no one had their hands on, and are using them against him in such a way that he can't find a way to beat them. Not only that, the reason that the Turks have these weapons is because he put his trust in someone who has betrayed him. Everything has thrown him for a loop. Suddenly, he realizes the people he believed in aren't necessarily the ones he should have been and the ones he didn't believe, he should have listened to more.

Leo and Lorenzo [Elliot Cowan] had a bit of a bromance happening. What have you enjoyed about that relationship this year?

Riley: Lorenzo goes through his own spiritual journey and cleansing this year. It puts the relationship -- which Leo thought was one of the most important in his life -- in real jeopardy. Lorenzo is going to lose trust in him. Everyone is going to lose trust in Leo because of what he brought down on Italy. Their relationships are going to be tested this year.

Leo's quest over the series has been to retrieve this Book of Leaves. How much are we going to learn about its origin, its purpose and Leo's intentions for it?

Riley: We're going to learn a great deal about the book. We're going to learn about its purpose. We're going to learn about what it can do and what Leo intends to do with it and what he intends to stop it from doing. Its origins are so shrouded in mystery and a lot of it is still left ambiguous, but we are going to get a far deeper understanding of it. Lots of questions from the first season will be answered.

Leo swings swords and gets into scraps. Can you preview which action sequence proved the most demanding?

Riley: There's so many. The first two hours are so intense. They are like a two-hour war movie. We have a brand new stunt coordinator this year and he was determined to make the fight sequences a lot more choreographed and a lot more complex as a result. They were incredibly difficult to pick up, but they looked fantastic on screen.

The trailer teases a huge battle with the Turks.

Riley: That was a long few days. We had an incredible set we built outside this time. A lot of the sets have previously been inside in our studio. We were outside in the Welsh weather over four to five days doing this fight. There were so many extras and stunt guys. Some had to be shipped in from London. It's a huge sequence and just when you think it's over, it begins again. I would say that was easily the hardest. Not only because it's dangerous -- things were going wrong, explosions were going off and one caught me in the face -- but it all pays off. It looks fantastic on screen.

Unfortunately, "Da Vinci's Demons" has officially been cancelled. How satisfying of a conclusion does the finale offer the fans?

Riley: That's the one thing we are really proud of. It's nice to have a show that's not going to leave people hanging. They are not going to feel like, "Oh God. I got caught in the middle of a gigantic cliffhanger like the last two seasons." There is a real wrap up and a sense of closure. All of the main characters get a fairly satisfactory conclusion to their arcs. There are still open-ended moments that the audience will want to fill in the blanks. It's bittersweet that it's ending, but exciting that we've been able to do it in a way that's not going to deflate the fans.

Ultimately, were you pleased with how the finale turned out?

Goyer: I was. I am. It's bittersweet. I'm pretty pleased with how the characters ended up. Some of them ended in more open-ended ways. Some of them ended with more closure, but it definitely felt like the closing of a significant chapter.

Goyer and your friend, Nicholas Holt (Beast in the "X-Men: franchise) are associated with superhero properties. Tom, have you ever auditioned for one and is that something that interests you?

Riley: Because there are so many of them, it would be hard pressed to find an actor who hasn't auditioned for Marvel or DC at some point. I think I went in for "Captain America" one time. I turned down an audition for Superman because I just thought, "That is never going to happen. Look at me." I went out for "Guardians [of the Galaxy]." There's so many of them, particularly with the MCU becoming such a gigantic world. I love those movies. I haven't been successful in auditioning for them in the past, but I have my fingers crossed that will change in the future.

Is there a superhero that would be a good fit for you?

Riley: I've been sniffing around Iron Fist. Aside from that, I don't know. "The Inhumans" are an exciting idea. There's so many. I'm open. Call me.

The complete third and final season of "Da Vinci's Demons" is now available to Starz subscribers via Starz On Demand and online on Starz Play. The third season premiere, "Semper Infidelis," airs 8 tonight on Starz.