A lot has changed for Kratos since he was last seen hacking and slashing his way through the roster of Greek deities. The new game sees the familiar anithero sporting a bushy new beard, an apt look for the series' new locale in the frigid wilderness of Norseland; new weapons now that he's lost his trademark, chained Blades of Chaos; and, most importantly, he has an adolescent son.

The change of tableau is not simply cosmetic, as the franchise's Grecian setting was integral to Kratos' story and was a fundamental aspect of the plot, characterization and even gameplay of the previous titles. The new location opens up the narrative to the wide breadth of Norse mythology, something of great interest to game director Cory Barlog.

"When I came back to the studio I knew I needed to make a big change to the game," Barlog explained to Heat Vision during a recent visit to the studio. "We had exhausted Greek mythology and kind of started to set up Kratos to be able to connect to more myths. We didn’t know exactly where we were going to go at the time, but we knew we were going to expand it out."

Barlog has been working on God of War since the first game in 2005, on which he was the lead animator. He moved up to game director for 2007's sequel, earning a BAFTA for his writing on the project, then served as game director for eight months on the third game before leaving the company. His return to the franchise (and developers Santa Monica Studio) came in 2013 where he put together a team to work on the next leg in Kratos' blood-soaked journey.

"When I really started forming the seed of this idea I knew it was going to be a massive polar shift for the whole franchise to really reimagine everything we can about it while still keeping the guts of God of War," Barlog said.

Changing up the setting was not the only shake-up Barlog had planned for the fourth installment, however. To match Kratos' new look, Barlog needed a new actor. Christopher Judge, perhaps best known for his role as alien military commander Teal'c on the hit sci-fi television series Stargate SG-1, won the role, replacing longtime Kratos voice actor Terrence C. Carson.

"The way we shot all the previous games, we were able to have a different body actor than the voice actor, so the voice actor could do most of their work similar to an animated film where they just did all V.O. work in the studio," Barlog explained. "Doing what we wanted to do with a camera that was never going to cut away, we had a lot of scenes that required two characters to interact physically on the stage. The size difference between Kratos and Terrence is very great. Offsetting that for the size of a child, it turned out it was going to be almost impossible to try and actually shoot them and go in and redo the animations."

Luckily, Judge had no such problem. Standing 6-foot-3 with the build of an NFL linebacker (Judge attended the University of Oregon on a football scholarship), he had the look of the character down. However, unbeknownst to the veteran actor, his fate ultimately lay in the hands of a 10-year-old: Sunny Suljic.

Suljic was cast as Kratos' son Atreus very early on in the game's development, when the actor was only 9 years old. The Atreus character was modeled after the young actor's stature and appearance, and when it came to finding his co-star, the team weighed Sunny's opinions about the casting of Kratos heavily.

"There was an audition and they asked me who I liked the most," Sunny, now 12, recalled as he took a break between recording sessions at Santa Monica Studio.

He was doing the one-on-one interview with Heat Vision as his mother waited around the corner ("She makes me nervous sometimes during these," he explained) when Judge showed up. A towering presence even to other grown adults, seeing Judge beside Suljic is an exhibition of true contrast. The massive actor immediately began rough-housing with his co-star, lifting him over his shoulders handily with one arm as Sunny giggled. The familial bond between them is evident instantaneously, a promising preview of the bond their roles require.

The laughter between the two was quick and genuine as they recalled the casting process. "We did a chemistry test, and I didn’t find out until later that they really did ask Sunny for approval," Judge said with a laugh. "If I had known then that my fate was in the hands of a 10-year-old," he turns to Sunny. "I owe you a pair of Nikes."

That relationship is all the more important when considering the amount of time both actors have worked on the project. Suljic has been recording motion and voice performances for over three years while Judge has been attached for two. The duo often perform their scenes together, sporting skin-tight suits covered in white balls, on a stage at Santa Monica Studio. That experience is clearly conducive to bonding.

"My sons now are adults and out of the house," Judge said as Suljic, beside him on the couch, looks (way) up at him. "The thing you always regret is that you can’t go back and spend more time with them at certain ages. "Being around Sunny just feels good to me. It’s feels like some of the time I missed with my own kids."

Stepping into a role already made famous by another performer can be daunting, but Judge saw the role as an opportunity to really bring something new to the character. "When I realized it was God of War, I did some background work on it," the actor said. "Terrence had played it for so long I thought it would just be a huge mistake to mimic his performance. I figured, well, if they’re recasting they’re going for something different or in a different direction. I just started with a blank slate and went from there."

That new direction extends to most other aspects of the game. Not only is Kratos now a father in a new land, but the gameplay reflects both the relationship between the two characters as well as the new Norse mythology.

"It’s most definitely not an escort mission," Barlog said, emphatically. To many gamers there are no two words more reviled than the dreaded escort mission. "It’s more like a military leader and a soldier that he’s teaching and taking under his wing," Barlog continued. "The player has direct command over Atreus and is trying to guide him through the process, but the kid has his own mind and he is able to handle himself even when you’re not paying attention." A button (square) on the controller is dedicated to Atreus, which allows players to direct him to different objectives which he will carry out on his own. "What we’re trying to do is kind of tap into that ‘teaching your kid to ride a bike as you run alongside’ thing," says Barlog.

For fans of the series, this is an extraordinary change of tack for Kratos' character — a man so driven by rage that he toppled the gods themselves to become the eponymous deity of conquest, battle and destruction.

"Kratos’ change in his play style is really this idea that he’s struggling with mastering this rage that he let out of the box in all the previous games. He was an angry monster who walked up to people and just killed them, didn’t even care," Barlog says. "I think Atreus is offering just this tiny bit of humanity that he lost long ago that allows him to not just kill somebody the first time he meets them and find out a little bit more."

For Judge, that nuance of character meant a meatier role. "When I first read this it kind of threw me because this was a real script. It wasn’t just a way to get into battles, it was really this great story of this relationship and this crazy mythology," he said before heading into a recording session.

Watching Judge — a jovial giant of a man who is quick with a smile and a rumbling laugh — transform into Kratos through the thick glass of a recording studio, it's easier to see how the actor scored the role. It takes him roughly three sentences and a whole bottle of Teavana iced tea to drop his already baritone speaking voice to the bassy thunderous grumbles of Kratos, yet he still maintains a patience in his delivery that was before unknown to the character.

"It's not a softer side, but a softer side to Kratos," said Barlog. "He has a very long road ahead of him before he can express the softer sides that we would associate with being softer, but he’s definitely a changed person."

No official release date for God of War has yet been announced. It will be available exclusively on PlayStation 4.