At the edge of the world, where the winter wind cut through the frosty fjords like an axe blade, lay the village of Bjornholm. The interwoven roofs of the cottages were covered with snow, and the smoke from the fireplaces mingled with the northern sky, lit by the glow of the aurora borealis. This is where Harald, Sigvald's son, grew up, dreaming of adventure and far-flung expeditions, as befits a true Viking. On that day, Harald left the family cottage early. His breath turned to steam as he ran across the frozen courtyard to the old harbour. The harbour was a place where mighty drakkars were built and sea stories circled like owls in the darkness. This morning, however, something was different. Fog shrouded the coast, and echoes of strange sounds carried across the water. Harald quickly found his friends Liv, the brilliant daughter of a blacksmith, and Einar, a fisherman's son who was not afraid of any storm. - Did you hear that? - whispered Harald. - 'What's that? - Liv squinted, trying to see something in the milky air. - 'Like singing... or calling from the other shore,' Harald replied, pointing a finger at the barely visible silhouette of an old boat swinging on its mooring. Einar shrugged his shoulders, but there was a shadow of concern in his eyes. - Maybe someone had returned from fishing and got lost in the fog. Liv, however, was of a different opinion. As they got closer to the old boat, they noticed that the deck was covered with a thin layer of ice, and there were clear boot prints on the planks. The footprints led to a steep path winding between snow-covered cliffs. Suddenly they heard a quiet whisper, like a breeze, but they were all sure it was no ordinary sound. Harald felt his heart beat faster. He took a step forward, and Liv and Einar moved behind him. The footsteps stopped at the entrance to a small cave, hidden among ice boulders. Inside was deep darkness, and from deep inside came metallic clatters, as if someone was pounding their fists against the rock. The friends paused on the threshold, uncertain whether to enter further. Harald was already about to suggest what they should do when a light flashed from within the cave and there was the deafening, dragging sound of a battle horn....