The tale begins in the halls of the Gjúkings, where Sigurd the Völsung, the slayer of the dragon Fafnir, had come to reside after his many adventures. Having tasted the blood of the dragon, Sigurd possessed wisdom beyond mortal men and a strength that was whispered about across all the Northern lands. However, his fate was entangled with the magic of Queen Grimhild, who sought to bind the hero to her family. Through a potion of forgetfulness, Sigurd’s memory of his previous betrothal to the Valkyrie Brynhild was wiped clean, and he instead wedded Gudrún, the daughter of Gjúki. To solidify their bond, Sigurd swore an oath of blood-brotherhood with Gudrún’s brothers, Gunnar and Högni, promising to support them in all their endeavors as if they were of the same womb.
Not long after these oaths were sworn, the talk of the court turned to the pursuit of a worthy wife for Gunnar, the eldest brother and King of the Niflungs. Gunnar’s heart was set upon Brynhild, the daughter of Budli, a woman of incomparable strength and beauty who dwelt atop a mountain in a hall surrounded by a flickering, supernatural flame known as the Vafrlogi, or the Wavering Fire. It was common knowledge that Brynhild had taken a vow: she would marry only the man who was brave enough and strong enough to ride through the wall of fire and reach her. Gunnar, though a noble and capable king, was not certain he could survive such a feat, yet his pride and desire drove him to attempt the journey. Sigurd, bound by his oath of brotherhood, agreed to accompany him to the mountain of Helagsfjället, where the trial was to take place.
Upon reaching the base of the peak, the air grew thick with the scent of ozone and burning pine. The sky above the mountain was perpetually illuminated by the orange glow of the magical barrier. The party approached the circle of flames, which roared with the intensity of a thousand forges. Gunnar mounted his finest horse and spurred the beast toward the heat, but as the flames licked at the horse's nostrils, the animal reared in terror, refusing to move even an inch further into the inferno. No matter how Gunnar cursed or used his spurs, the horse remained paralyzed by instinctual fear. Seeing this, Sigurd offered his own horse, Grani, a descendant of Odin’s eight-legged steed Sleipnir. Grani was a horse of divine lineage, possessing a spirit that did not know the meaning of cowardice. However, when Gunnar mounted Grani, the horse remained rooted to the spot. Grani knew his master, and he would only bear the weight of the man who was destined to cross the fire.
Desperation took hold of Gunnar. He knew that if he returned empty-handed, his reputation would be tarnished, and he would lose the woman he desired above all else. It was at this moment that the cunning magic of his mother, Grimhild, which they had brought with them in the form of ancient runes and spells, was put to the test. Sigurd and Gunnar stepped aside, away from the eyes of their retainers. Through the use of powerful shape-shifting sorcery, the two men exchanged their physical forms. By the power of the spell, Sigurd took on the height, the face, and the voice of Gunnar, while Gunnar assumed the likeness of the dragon-slayer. This deception was intended to trick not only the flames but also Brynhild herself, who would believe she was being won by the King of the Niflungs.
Now appearing as Gunnar, Sigurd mounted Grani once more. The horse, sensing the true spirit of his master beneath the borrowed skin, neighed with a sound like a trumpet and charged forward. As they hit the wall of fire, the flames flared up to the very heavens, the heat enough to melt iron, yet Sigurd did not flinch. The Vafrlogi responded to his courage, parting just enough to let the hero pass through. Inside the circle of fire, the world was strangely silent. The roar of the flames became a dull hum, and the air was cool and still. Sigurd, in the guise of Gunnar, rode up to the doors of the hall and entered. There he found Brynhild, sitting upon her throne, armored and majestic. She was astonished to see a man had breached the barrier, and though she felt a strange, nagging familiarity in the presence of this visitor, she was bound by her oath to accept the man who had ridden the fire.
Sigurd stayed with Brynhild for three nights in the hall. To ensure his loyalty to the real Gunnar and to maintain the sanctity of the marriage he was winning for his friend, Sigurd placed his bare sword, Gram, in the bed between them each night. He told Brynhild that his oath forbade him from touching his bride before the formal wedding feast in his own kingdom. During these three days, they spoke of many things, and as a token of her pledge, Brynhild gave him a ring. This ring was none other than Andvaranaut, the cursed gold ring that Sigurd had taken from the dragon’s hoard, unaware that he was giving away a token that would eventually reveal his lie. In exchange, Sigurd gave her a ring from the Niflung treasury, sealing the contract of marriage.