Later this month, The Lord of the Rings: The Rings of Power will take viewers back to live-action Middle-earth. But that’s not the only adaptation of J.R.R. Tolkien’s mythology coming to screens this year, and you can now watch the first trailer for Lord of the Rings: The War of the Rohirrim. Directed by Kenji Kamiyama, this anime film is set to hit theaters this December.

The War of the Rohirrim adapts a story from the history of the kingdom of Rohan, described by Tolkien in the appendices to The Lord of the Rings. As the trailer explicates, this story is set around 200 years before the War of the Ring, a.k.a. the conflict against Sauron detailed in Lord of the Rings proper. The narrator of the trailer (and the film itself) is Miranda Otto, who originally played Eowyn, shieldmaiden of Rohan and killer of the Witch-King, in Peter Jackson’s Lord of the Rings film adaptations.

War of the Rohirrim is about a man who ruled Rohan long before Eowyn’s time: The legendary king known as Helm Hammerhand (voiced by Brian Cox). When Freca (Shaun Dooley, the chieftain of neighboring Dunland) proposes that his son Wulf (Luke Pasqualino) wed Helm’s daughter Hèra (Gaia Wise), Helm reacts badly. He strikes Freca dead with a single punch (hey, they don’t call him “Hammerhand” for nothing) and Wulf vows revenge. Sure enough, a few years later, Wulf returns with an army of Dunlendings, and brings Rohan to its knees. Helm and his people seek refuge in the fortress that will one day be named Helm’s Deep in his honor.

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Courtesy Warner Bros. Pictures

What makes The War of the Rohirrim an especially interesting adaptation is that it revolves around the character of Hèra, who was originally unnamed in Tolkien’s text even though the proposal for her hand in marriage is what kicks everything off. Producer Philippa Boyens (who previously co-wrote Jackson’s Lord of the Rings films) decided to focus the whole story around Hèra.

“We know Helm has a daughter, and we know that she was central to the conflict that happened. But myself, and especially screenwriter Phoebe Gittins, were drawn to her,” Boyens told Entertainment Weekly earlier this year. “We could feel the weight of being that unnamed daughter, which immediately piqued our interest: Who was she? How did she live?”

The trailer gives us a taste of the answers to those questions. With her flowing red hair and her facility with animals like horses (the pride of Rohan) and even a giant eagle, Hèra resembles the heroine of Hayao Miyazaki’s seminal film Nausicaä of the Valley of the Wind. But the trailer indicates we should also expect direct callbacks to the main Lord of the Rings narrative, as it ends with people searching for as many rings as they can find.

Courtesy Warner Bros. Pictures

Watch the trailer above. The Lord of the Rings: The War of the Rohirrim hits theaters on Dec. 13.