"Odin" utilised a hologram projection to make himself appear human, and adopted the name and guise of Odin, the Norse god, when he presented himself to the inhabitants of a Viking village his army had targeted. Inviting the warriors of the village to dine with him in the halls of Valhalla, he in reality transported the Vikings aboard his spaceship, where they were later killed. The adrenalin and testosterone extracted from the warriors during their deaths were transformed into a fluid - dubbed "warrior juice" by Clara Oswald - consumed by the Mire for sustenance.
"Odin" also transported Clara and Ashildr aboard the Mire spacecraft, but spared their lives after realising they possessed the sonic sunglasses, fearing the superior alien technology they represented. Although almost persuaded by Clara to leave the Earth in peace, he was incited by Ashildr's declaration of war against the Mire to stay and fight. He gave the remaining people of the village a single day to prepare.
When "Odin" arrived in the village with ten Mire footsoldiers the following morning, he found the villagers not preparing for combat, but partying and dancing. Confused, he failed to realise that the celebration was a distraction; the villagers, under the command of the Twelfth Doctor, had constructed an elaborate trap for the Mire, which involved using electric eels and metal wiring to play havoc with their equipment. The plan culminated in Ashildr using a stolen Mire helmet to project the image of a terrifying sea dragon over a harmless wooden puppet, which the Mire were convinced was real. Outmatched, they fled to their ship, leaving their leader alone.
Afterwards, the Doctor revealed the truth of the deception, and also revealed that Clara had recorded the entire humiliating defeat on her mobile phone. On danger of having the footage uploaded to the Galactic Hub, "Odin" and the rest of the Mire fled the planet, promising to one day enact vengeance. (TV: The Girl Who Died)