Fafnir

In Norse mythology, the dwarf Fafnir was one of three brothers. He didn’t begin life as a dragon, but became one after murdering his father for gold. He hid in the wilderness with the treasure, and became a dragon in order to better guard it. Unfortunately for the upstart dragon, he also happened to breathe poison around the land, which the locals understandably weren’t too happy about.

Fafnir’s brother, the blacksmith Regin, asked his own step-son—the young hero Sigurd—to kill the problematic dragon. Sigurd decided to dig a ditch, hiding there with the aim of suddenly leaping out and stabbing Fafnir in the heart.

Odin, King of the Gods, for his own reasons turned up and advised Sigurd to dig a number of other ditches to drain away the dragon’s blood, so that he wouldn’t drown. Sigurd listened to the advice, and when Fafnir showed up he duly attacked him. Though he missed the heart (instead plunging his sword into the dragon’s shoulder), the wound still turned out to be fatal.

Regin then asked Sigurd to cook the dragon’s heart. Sigurd, for some reason seeing nothing odd about this, did as he was told. He touched the heart to check if it was cooked, and burned his thumb in the process; and when he touched his thumb to his mouth in order to ease the pain, he suddenly found that he was able to understand the speech of birds. These birds told Sigurd that Regin intended to kill him, so the young hero killed Regin first, and made off with all of the gold himself.