The year is 895AD in the North Atlantic, King Aurvandill and his bastard brother
Fjölnir return to their kingdom with chests full of riches after his overseas conquests.
Aurvandill reunites with his wife Gudrún and his son Amleth, who is gifted a special necklace
that Aurvandill took from a prince he killed. Fjölnir also reunites with his baby son Thorir,
yet his mood quickly gets sour when the court jester Heimir makes fun of him. After the banquet,
Aurvandill spends some time with Gudrún and shows her where he's been wounded. Gudrún worries,
but Aurvandill tells her he'll be fine for now because he doesn't plan to die like an invalid,
he'll die with honor in combat. He does admit, however, that he should get Amleth ready in case
the worst happens. Later that night, Aurvandill takes Amleth with him to the temple so the boy
can go through a spiritual ceremony to officially become a man, all overseen by Heimir. Father and
son channel their inner wolves and Amleth is blessed with the knowledge of the tribe, for
which he must swear to live with honor and avenge his father if he ever falls to the enemy's hands.
The drink Heimir gives Amleth causes him to see a series of hallucinations,
and when he touches his father's wound, Amleth gets to witness the entire family tree. The two
of them leave the temple in the morning and are ambushed by a group of masked warriors on horses.
Amleth wants to help, but Aurvandill tells him to run away, and the kid hides behind a rock to
watch how his father is hit by multiple arrows. The leader of the group then takes his mask off
and reveals to be Fjölnir, who proceeds to kill his brother to take his place as king.
Afterward, he sends his soldiers to find Amleth, who runs away deeper into the forest.
He's suddenly found by Finnr, but Amleth manages to cut off his nose with a knife before pushing
him off and escaping. A few moments later, Amleth makes it back to his village, where soldiers are
killing anyone that still supports Aurvandill and Fjölnir is kidnapping a screaming Gudrún.
Finnr doesn't want to admit he lost to a child, so he tells Fjölnir that Amleth is dead and his
body was thrown at sea. Having seen enough, Amleth goes to the coast and steals a boat as he swears
to one day avenge his father and save his mother. Many years pass, and now an adult Amleth lives in
the Land of the Rus as a berserker with a tribe of Vikings. He's left his prince life to become
a fearsome warrior that helps his band raid villages, kill their soldiers, claim the women,
and gather young people to be sold as slaves. After the successful raid of Gardariki, Amleth
leaves the celebrations behind to take a walk and comes across a temple with a Seeress inside.
This Seeress reminds Amleth of his revenge oath and predicts he'll be victorious,
but for that to happen, he must go to the land of the north where Fjölnir currently resides. He must
also follow a vixen to seek a fated sword that will match his rage. The Seeress disappears after
clarifying that she's only helping him because his path is intertwined with a Maiden-King. The next
morning, Amleth hears the slaves they've captured will be sent to Iceland to work for Fjölnir and
takes the chance to gather some information about his uncle. It turns out he fled to the backwater
with his family after the King of Norway took his kingdom, so he killed his brother for nothing. At
that moment, Amleth sees a raven, and remembering his father used to be called the Raven King,
he takes it as a sign. Coming up with a plan is easy: Amleth cuts his hair, hides his necklace,
steals some different clothes from a body, and brands his chest with the slave mark before
sneaking aboard the ship that will take the slaves to Iceland. There, he meets Olga, who claims to
be a sorceress. She knows Amleth is actually a Northman, but she still treats him kindly,
and even comforts him when at night his dreams are haunted by visions of the past, the future,
and Olga herself. The ship is shaken by a storm on the way, but the party still manages to make
it safely to Iceland. They're picked up at the shore by Finnr, who puts all the slaves in chains
and guides them to Fjölnir's farm, where he lives with a now-adult Thorir and his second son, the
young Gunnar. Fjölnir isn't impressed by how weak these slaves look and wants to send them away,
so Amleth hits the man next to him to show off his strength and introduces himself with a fake name.
Fjölnir decides to keep him, and he also chooses two men for the fields and some maids for his
wife, taking particular interest in Olga. On his first night at the farm, Amleth sneaks out to try
to steal a knife, but gets distracted when he sees a vixen on the field just like the Seeress
had predicted, which means he's on the right path. The next day, Amleth plays along and works hard as
a slave, which gives him the opportunity to enter Fjölnir's home and make a shocking discovery:
Gudrún is there, alive and well. She was the one to give birth to Gunnar as Fjölnir's new wife.
Afterward, Olga checks on him to see if he's gathered information,
and when soldiers see her out of her station, they come to take her
away. Right before they arrive, Olga asks Amleth to come looking for her if he ever loses her. When
night falls, Amleth follows the vixen and finds a He-witch inside a cave.
This man instantly recognizes Amleth and shows him he's kept Heimir's head since Fjölnir killed him.
Through a special ritual, the He-Witch summons Heimir's spirit and gets the head
to talk directly into Amleth's mind to tell him the tale of the legendary sword Draugr,
which can only be unsheathed during the night. To find it, Amleth must visit the sword's owner, the
Mound Dweller, and be sure to trust the moonlight. The He-Witch also offers Amleth one last prophecy:
one day he'll have to choose between kindness for his kin or hate for his enemies. Next,
Amleth enters a mound and finds the body of the Dweller, who is sitting with the sword on his lap.
As soon as Amleth tries to take the sword, the Dweller awakes and begins attacking him,
so Amleth must defend himself with any trash he can find around him. When the Dweller walks
around the ray of moonlight that slips through the mound's entrance, Amleth remembers the He-Witch's
words and pushes the body under the light. The Dweller freezes and gives Amleth the chance to
kill him, but as soon as he turns around, Amleth finds himself back at the beginning in front
of the sitting man. This time, when he tries to take the sword, he retrieves it without issues.
Amleth returns to the farm and is seen by Fjölnir's dog, who starts barking.
To make him shut up, Amleth growls at him, getting Fjölnir to dismiss the barking as unimportant and
to miss Amleth. Then, Fjölnir goes looking for Olga to spend the night with her, but Olga shows
him it's her period, meaning she isn't available. She also tries to attack Fjölnir, but he just
easily pushes her aside and orders the head maid to teach Olga some manners before leaving.
Amleth sees all this from his hiding spot and thinks it's the perfect moment to attack,
but the sun is rising and he can't unsheath the sword, so he hides it until the right time comes.
The next day, Amleth tells Olga about the sword, and she agrees to help because she wants her
freedom too. She has access to the kitchen, but Amleth makes sure to clarify something: he intends
to rescue his mother as well. Gudrún is just another victim, and she plays along with Fjölnir's
wishes for the sake of her safety and Gunnar's. Afterward, Fjölner takes his family and a selected
group of slaves to meet with the chieftain and his people for a match of knattleikr.
The game consists of two teams of five warriors that fill fight over a ball in order to score,
and killing is allowed. Amleth is chosen for Fjölnir's team and finds himself in a brutal sport
where little by little each player dies. Towards the end, only Amleth and one very big opponent
are left. Fjölnir's team is losing and that drives Gunnar mad, so he tries to steal the ball to score
and is attacked by the opposite team's player. Gunnar is knocked out, but before he gets killed,
Amleth jumps in his defense and kills his opponent. Later during the celebrations,
Thorir approaches Amleth to congratulate him for his loyalty and bravery. As a reward, from now on,
Amleth will have privileges at the farm: he'll work less, command the other slaves, and be
allowed to choose a woman for himself. Thorir tells him he's even allowed to choose Olga because
Fjölnir has given up on her and her attitude. Amleth doesn't think about it twice and looks
for Olga, then takes her deep into the forest so they can get busy without anybody else watching.
Once they're done, Olga uses her abilities to talk to Mother Soil and ask for her protection.
They also find some special mushrooms that will help them with their plan for revenge which will
finally start when they return to the farm. The next day is spent working normally, but
when night falls, Amleth ambushes two of Gunnar's companions and kills them. With their body parts,
he makes a centaur form and leaves it to be found by the leaders in the morning. Gunnar is obviously
furious when he sees it and swears revenge on the Christians, believing it was them that did this,
but Fjölnir is doubtful. The farm's priestess checks the bodies and informs everyone that
the wounds aren't from this world - whoever did this, it's hungry for more and will attack again.
Later at night, while the priestess prepares a girl to be sacrificed to the gods for protection,
Amleth provokes all the animals in the area into barking and howling.
This drives Fjölnir's dog mad and causes him to attack his master, so Fjölnir has to kill him in
self-defense. While everyone is distracted by the animals, Amleth enters the temple,
frees the girl, ties up the priestess instead, and kills the priest before hanging him at the altar.
The following day, while Amleth secretly adds the mushrooms to the stew, the male slaves are given a
new chore: they will protect the farm from any incoming attack. In the evening, Fjölnir's men
begin hallucinating, which causes them to attack each other or even themselves. After talking to
Olga to agree on a meeting spot at dawn, Amleth sneaks inside the main house and surprises his
mother by revealing his identity. Gudrún is proud to see him alive, but she's got shocking news for
him: she doesn't need to be rescued. Aurvandill had lied to Amleth when he told tales of his
romance with his wife, Gudrún had actually been a slave that the king took by force.
She never loved him or mourned him, in fact, she was the one that begged Fjölnir to kill him. The
day of the betrayal, she hadn't been screaming, she had been happily laughing because she finally
was with the man she actually wanted. Amleth's starting to think he should kill Gudrún as well,
but she reminds him that he's a man full of love for his mother and his brother. If he kills
Fjölnir and Thorir, Gudrún would accept Amleth as her new king and they could rule together.
She goes as far as kissing her own son, but Amleth doesn't fall for it and leaves her behind
to find Thorir, who he kills on his bed. Then he meets with Olga to tell him he'll be hiding
in the hills because Gudrún knows his identity and he can't play the role of a slave anymore,
so they'll finish their plan the next day. In the morning, Fjölnir is mad with grief
when he finds Thorir's body without the heart, and Gudrún tells him Amleth did it.
Fjölnir decides to start killing slaves to make them confess what they know, but when he is about
to kill Olga, Amleth reveals himself to stop him. He's wearing his prince necklace again and,
after using his real name, he shows that he has Thorir's heart. Fjölnir sends his men after him,
and Amleth meets them in combat to give Olga time to escape, then he allows them to capture him.
Thinking himself victorious, Fjölnir takes Thorir's heart back, but Amleth reveals it
actually belongs to the dog. Furious, Fjölnir hangs Amleth in the barn and beats him up to make
him confess the location of Thorir's heart, but Amleth refuses to tell. Fjölnir needs to leave for
Thorir's funeral but promises to come back later to finish things, and on their way out, one of the
men drops Amleth's sword on the ground thinking it's useless because it can't be unsheathed. As
soon as everyone's gone, a group of ravens shows up with a hooded figure, and they free Amleth. The
people of the farm give Thorir a proper ceremonial funeral and Gunnar is declared the only heir to
the throne. Afterward, they go back to the barn to kill Amleth, but by the time they get there,
he's already gone. Meanwhile, Amleth finds himself on a horse ridden by a valkyrie that is taking him
to Valhalla, but suddenly he wakes up and realizes it was Olga that saved him. The fact she came back
for him must be a sign of fate, inspiring Amleth to run away with her. He's got kinsmen in Orkney,
so they could find passage there. After a day of horseriding, the couple finds a boat and is
allowed aboard. Amleth notices Olga has a scar on her neck that Fjölnir left there with his knife
and decides to kiss it for comfort; this act gives him a vision of the family tree again. Thanks to
this, Amleth learns Olga is pregnant with twins, and one of them will be the Maiden-King from the
Seeress' prophecy. This should be good news, but Amleth fears that his children will never
be safe as long as Fjölnir lives. Remembering he was told he would have to choose between kindness
for his kin or hate for his enemies, Amleth decides to choose both. Ignoring Olga's pleas,
he gives her his prince necklace so she can secure her future and jumps off the ship. While Amleth
swims back to the shore, Olga calls the wind spirits to protect the ship's journey. When night
falls, Amleth sneaks back into the farm and begins killing all the warriors, taking extra pleasure in
slowly finishing Finnr through what's left of his nose. After freeing all the women, Amleth enters
the main house and is attacked by Gudrún who is wielding a sword Fjölnir left her for protection.
However, she has no warrior training, and it's incredibly easy for Amleth to kill her with a
sword through the heart. At that moment, Gunnar shows up and jumps on Amleth's back to stab him
a couple of times, but Amleth shakes him off and quickly kills him as well. Fjölnir shows up next
and, as he picks up the bodies of his family, he asks Amleth to meet him at the Gates of Hel,
meaning the crater of the volcano Hekla, for a final proper duel. Bleeding heavily from the stab
wounds, Amleth watches the slaves burn down the farm before leaving for the volcano. On his way
up to the crater, Amleth finds the bodies of Gudrún and Gunnar, so he gives them his blessing
before finally meeting with Fjölnir. Both men are outstanding warriors and the battle's pretty
balanced at first, but Amleth is already hurt thus it doesn't take long for Fjölnir to overpower him.
However, Amleth finds strength in his anger to rise again and, after exchanging a few more blows,
both men kill each other at the same time. As he passes out, Amleth has a vision of
Olga with his twins before a valkyrie appears to take his soul through the gates of Valhalla.