Stephen Lang says his Avatar: Fire and Ash character Quaritch fits with the Ash People because "he's in familiar territory" with the war-hungry Na'vi

Things haven't been easy for Colonel Miles Quaritch. After dying in the first Avatar movie, he reappeared in Avatar: The Way of Water as a recombinant, which means his human memories were implanted in the body of a Na'vi – the native Pandoran species Quaritch is sworn against.

In Avatar: Fire and Ash, we see a whole new side to Quaritch once again. This time, he becomes tangled up with the Mangkwan Clan, or the titular Ash People, a bloodthirsty type of Na'vi obsessed with fire who are led by the fearsome Varang. Surprisingly, Quaritch seems to have a certain affinity with these unlikely new pals.

"He must adapt to Pandora will he or nill he. He's tried to make Pandora adapt to him," Lang tells us when we meet in London. "He brought in a certain consciousness when he was head of security at Hell's Gate. And, as he acknowledged very early on, 'My job is to keep you alive, and I will not succeed.' So, he was kind of doomed and consigned to failure from the very beginning. That whole thing has changed, now.

"He's become, I shouldn't say one with the planet, because he hasn't – or one with the moon – but now he has the DNA of Eywa, [it's] actually coursing through his veins, so he needs to find a way to adapt that's acceptable to the Quaritch that's left in him," he continues. "And, of course, the Mangkwan, the Ash People, represent that, because when he goes to where they live, he's in familiar territory. The very sulfurous smell of conflict and war is in the air. This is something that he understands. This is a milieu in which he exists."

Jake Sully, though, believes Quaritch is capable of becoming one with Pandora, and throughout the new film, frequently encourages his nemesis to open his heart to the natural world around him.

"Well, there's been a definitely an evolution in the relationship, a deepening of the relationship, and, in some sense, there's been a widening of the chasm between them," says Lang of Quaritch and Jake's complicated dynamic. "But, on a whole 'nother level, there's sort of almost a mutual dependence that has occurred, it seems to me. And, of course, they're bound together by this young boy, Spider, as well. So, whatever exists between Quaritch and Sully, just because of the fact that they're both Marines, they're both mission oriented, they both understand – they both have the same vocabulary, it seems to me. There's this added thing of this boy, and are they vying for him? What exactly is it? That dynamic is constantly shifting between them, and so much of the joy of making a film like this is exploring that dynamic."

But, of course, you should still expect Quaritch and Jake to trade blows. "There's a battle royale at the end, a real donnybrook that happens, and there's always a fight between Sully and Quaritch in these films," says Lang with a grin. "So, somehow you've got to keep kind of upping it. The ante goes up, and each one is different. It's like thinking back to the heavyweight fighters that we love, thinking about Muhammad Ali, or Tyson. Each of their fights is brutal, and in different ways. They're articulated in different ways, and I think Ali and Frazier fought three times. It's like Sully and Quaritch, just kind of going at it."

You can watch Jake and Quaritch clash when Avatar: Fire and Ash arrives in theaters this December 19. In the meantime, check out our guide to the biggest movie release dates of this year and beyond, or catch up on the previous film with the lowdown on the Avatar: The Way of Water ending explained.