This is stylization of the world-famous carving "Sigurd the Slayer of Fáfnir" on portal plank from Hylestad stave church.
Also these events are described in epic poem The Nibelungenlied.
more info https://en.wikipedia.org/wiki/Fafnirhttps://en.wikipedia.org/wiki/Sigurd

Metal: sterling silver (925)
Weight: approx. 24 g (0,84 oz)

Description:
Sigurd roasts the heart of the dragon
The fourth scene, which is on the second door panel, shows Sigurd roasting the heart of the dragon and sucking his thumb while Ragin appears to sleep.
After slaying Fafnir, Regin asks Sigurd to take the dragon's heart and roast it for him. "Regin then lay down, drank Fafnir's blood and went to sleep." Sigurd himself then touched the heart to see if it was cooked, but the boiling blood ran down his hand, scalding him. When he drank the dragon's blood, he was able to hear "the speech of birds." From the birds, which are depicted in the fifth scene, he heard of Regin's plot to kill Sigurd, in "vengeance for his brother."

Sigurd kills Regin
In the sixth scene, Sigurd slays Regin with his sword. Sigurd, both warned by the birds of Regin's plot to betray him and encouraged by their assertions that great wealth, knowledge, and power would be his if he killed Regin preemptively and took possession of Fafnir's treasure, kills Regin. Sigurd, convinced by their counsel, states "It will not be my ill fate that Regin shall be my death. Rather, both brothers should go the same way." Sigurd decapitates Regin using the sword Gram.

Grani carries the treasure
In the fifth scene, Sigurd's horse Grani stands carrying a chest containing Fafnir's expansive treasure and two birds are depicted below Grani perched in the branches of a tree. The birds likely belong to the group whose speech Sigurd understood. This scene combines elements of the legend that took place before and after the slaying of Regin.

After killing Regin, Sigurd mounts Grani, and rides to Fafnir's lair, where he finds "an enormous store of gold" from which he takes "many precious things" including the helm of terror and the sword Hrotti specifically. Sigurd loads large chests with the treasure onto Grani, despite expecting that it would be too large a load even for a pair of horses. Grani carries the treasure without difficulty, even refusing to move until Sigurd rides on his back, running "as if unencumbered.

Gunnar in the serpent pit
The last panel shows Sigurd's brother-in-law, Gunnar, in a snake pit playing the harp with his feet in an attempt to pacify the snakes.
Fafnir's treasure is cursed. In his dying breaths, Fafnir warns Sigurd that his gold "will be the death of all that possess it." Sigurd, is unfazed by this and mentions the mortality of all men. After Sigurd's death at the hands of his three brothers-in-law, Gunnar, Hogni, and Guttorm, Fafnir's treasure is hidden by Gunnar, sunk to the bottom of the Rhine. Gudrun remarries, to Atli (Atilla the Hun), who is fascinated by the treasure and seeks to own it. Gunnar refuses to tell Atli its location, insisting, "Rather shall the Rhine rule over the gold than the Huns wear it on their arms." Atli orders Gunnar to be placed into a serpent pit, with his hands bound behind his back. Gudrun sends her brother a harp, and Gunnar is able to play "so exceedingly well" with his toes that he lulls the snakes to sleep, "except for one large and hideous adder" who kills Gunnar in a single strike