Kvasir's Mead is a special beer made from the blood of Kvasir mixed with honey. It is the most coveted drink in the Nine Worlds of Norse mythology. When someone drinks the mead, they become poetic for a short span of time.
Kvasir was a wise and friendly god who loved to help and advise others on various matters. One day, the dwarf twins Fjalar and Gjalar invited him to their home. Unfortunately, they had malicious intentions. They brutally murdered Kvasir. The gods then used his blood to create Kvasir's Mead.
Magnus Chase comes to know from Aegir that he needs to drink Kvasir's Mead if he needs a chance at defeating Loki in a flyting. Magnus promises to give Aegir a portion of the mead when he defeats Loki. Njord later tells him more about the fabled mead and its origins. When Magnus and his friends arrive at York, they meet the giant Hrungnir, who claims to know the location of Kvasir's Mead. Magnus, Alex Fierro and Thomas Jefferson Jr. manage to defeat the giant and his magical sculpture in a duel. Hrungnir then reveals that a portion of the mead is available in Flåm, Norway. There, they meet Frigg, who tells them that the mead is at a secret place owned by Baugi. Magnus, Mallory Keen and Samirah al-Abbas discover the secret place - a waterfall. They manage to defeat the thralls guarding the location using the Whetstone, which they had obtained earlier. They manage to talk to Gunlod, the giantess imprisoned inside the waterfall. With the help of Mallory's Serrated Knife, they are able to obtain a small amount of Kvasir's Mead from Gunlod. They accidentally trigger an alarm, as a result of which Baugi and Suttung arrive there. The heroes, with Halfborn Gunderson and Sumarbrander's help, manage to defeat the giants and return to their ship.
Later, when the heroes are about to leave for Naglfar from the Fortress of Skadi, Magnus drinks the mead. He doesn't feel very poetic earlier. However, at the flyting with Loki, he gradually gains confidence and poetic talent as he begins to praise his friends and describe their achievements and his own contributions. Even Loki's army, led by Captain Hrym, begins to appreciate Magnus's incisive verbal attacks on Loki. Eventually, Loki is defeated. Stripped of his confidence, he becomes very small in size. Mallory moves quickly and traps him in the walnut that Frigg gave her. The heroes go to Vigridr and hand over the walnut, with Loki inside, to the gods. Magnus realizes that he has finished the mead he had fully and that he had nothing to give to Aegir. Odin later reveals that the gods have a reserve supply of Kvasir's Mead and he promises to give a small portion of that to Aegir.