The Astrid-Thing was a Thing assumed the form of Astrid, who was a villager of the ruined town the Vikings stumbled upon. The Astrid-Thing is responsible for the dilapidated state of the town, and the deaths of Bjorn Grimshaw and his army.
The Astrid-Thing came into being after being assimilated an unclear amount of time before the events of The Northman Nightmare, as well as four other women. The five then laid siege to the entire town, killing nearly all of its inhabitants. She encounters Rodmar and his crew when they entered the village, and is nearly revealed by Finn, who is killed as he tries to flee. During the night, it lures out and assimilates Erik, a member of Rodmar's crew. In the morning, after the death of the Finn-Thing, Astrid and the other four women flee the village, but not before one of the Astrid-Thing's braids is lost. After the vikings leave the village to burn, they spot the Astrid-Thing mid-transformation. When a herd of bison accidentally damage the spaceship buried under the ice and snow, the Astrid-thing springs from the flames and attacks, sporting half of Erik's face. However, it is ultimately subdued and presumably killed when the rest of the spaceship crashes and is destroyed.