The Oseberg Serpents are a species of legendary serpentine beasts which acted as the main antagonists of the 2013 Norwegian monster film Gaten Ragnarok.
In the day of Vikings, the King of Norway was determined to seek out a secret island called the Eye of Odin in the middle of a lake in the northern portion of Norway, which rumors say held secrets about Ragnarok, an event that would trigger the world's destruction. The King and his army first had to deal with the guardians of the island, a large member of serpents native in the area, which they attempt to lure out of the water with a sheep. Despite his daughter's pleads, the King remained adamant in their quest before the serpents emerged from the water and engaged the army, leaving it ambiguous of their fates.
In the modern day, archaeologist Sigurd and his crew travel to said lake in hopes of finding ancient Viking artifacts. Arriving at the Eye of Odin, they discover a cave containing a Viking helmet and other objects. Around this time, Sigurd's son Brage finds a cylindrical stone and packs it into his bag. The tour guide Leif suddenly demands the artifacts at gunpoint and leaves the group trapped on the island. As he paddles across the lake, his raft is taken out from below by one of the serpents who is alarmed by their intrusion.
That night, as Elisabeth and Sigurd's kids sleep in an abandoned Russian barracks, Sigurd and Allen return to the cave to explore deeper, following a tablet written on a stone. They discover the pit of the cave containing skeletons of humans from many eras of time, and spot the Mother Serpent (possibly the same serpent who confront the King and his men in the film's prologue) slithering down the cave from behind the rocks. Horrified by this discovery, and realizing the clues the King's daughter left behind were in fact, warning against threatening these creatures, they soon made haste for the rest of their party on the outside.
Meanwhile, Brage's stone, which turned out to be one of Oseberg Serpents' eggs, hatches, with the emerged baby terrifies the children and prompted Elizabeth to confine it within a metal box. However, its cries rattles the barrack's cable, alarming its mother who pulled it underwater to save its young. Fortunately, Allen and Sigurd managed to rescue the group before the housing plummets into the lake, all while unaware with the baby serpent's presence in the box until Allan discovered it. Though surprised, Allan chose to kept others in the dark about his discovery for his own purposes.
Another adult serpent emerges from the water in the attempt to attack Elisabeth and Sigurd when the latter successfully fixed the zipline. It then made another attempt to take their live upon seeing the two survived the attack, but is stopped by a shot on its eye in courtesy of Allan. Mother Serpent soon takes the matter into its own hands to chase the group, where it kills Allan who attempted to escape with baby serpent inside the box but losing it and knocked Sigurd and Elizabeth out cold by accident. It then proceeded to threaten Sigurd's children, demanding the whereabouts of its child. Fortunately, Sigurd, who discovered the baby, arrived in time to return it to its mother, who then spared the group with its child safe.
In the light of the encounter, Sigurd, who have managed to solve the mystery of Oseberg Ship, tells his boss the story about their adventures, but not disclosing fates of their deceased guide and Allan and advised the museum to conduct the search at the south of Bergen (the area where Eye of Odin located at) to ensure no one disturbs the serpents to prevent future incidents.