Like last year’s Oscar-winning Birdman, Alejandro Gonzalez Iñárritu’s latest effort is also rather ambitious. The director has been in production on The Revenant since last September, choosing to shoot the film using only natural light, which made the experience rather difficult for both the cast and crew. Following the release of the very impressive first trailer, Iñárritu and leading man Leonardo DiCaprio are opening up about what we can expect from the upcoming film — and what we shouldn’t expect.

Here’s what you shouldn’t expect from The Revenant, according to Grantland’s profile on the film: DiCaprio’s character has very little dialogue, similar to his co-star Tom Hardy’s role in Mad Max: Fury Road.

“It was a different type of challenge for me,” DiCaprio says, “because I’ve played a lot of very vocal characters. It’s something that I really wanted to investigate — playing a character that says almost nothing. How do you relay an emotional journey and get in tune with this man’s angst … without words?”

In addition to the challenges presented by such an action and reaction-based character, The Revenant also faced difficulties with shooting in available, natural light:

“To pull off these complicated sequences, like a ballet, movement needed to be precise,” DiCaprio says. “When it came down to that nail-biting moment to capture that magic light, every day was like putting on a mini-piece of theater. If we lost that one hour, if we didn’t accomplish what we had to accomplish, we were there the next day. And oftentimes many of these locations were very remote. So it was a very intense set, because we knew we only had one shot every single day. Otherwise … we would be back there again.”

And then there was the issue of Mother Nature herself, who prevented Iñárritu & Co. from completing the final scene, which they will finish over the course of about a week in Ushuaia, in the Tierra del Fuego region of Argentina:

“The snow melted down, literally, in front of our eyes,” Iñárritu says. “We experienced global warming; we were planning to shoot the ending scene in a location that supposedly will have snow …” he laughs. “[But there were] bees. So we had to shut down.”

The Revenant is based on the true life story of Hugh Glass, a frontiersman in the early 19th century who was attacked by a bear and left for dead by his companions. Glass then sets out to seek revenge on his former friends, but Iñárritu fictionalized the story a little to hopefully make Glass more empathetic:

“Revenge is a feeling [that] when you commit it, it leaves you empty. It’s not a wholesome emotion, and it’s not satisfying.” His stakes-raising solution was to create a son for Glass, named Hawk, by a relationship with a Pawnee woman: “I thought that a father-son relation, a filial relation, is much more complex and fulfilling — more empathy.”

The Revenant hits theaters on December 25 opposite The Hateful Eight — giving us not one, but two gritty, wintry movies to look forward to this holiday season.