dwarf
Brokkr
The dwarf who bet Loki his head that his brother could out-forge Ívaldi's sons, worked the bellows while a fly stung him, won, and sewed Loki's lips shut.
Brokkr is the dwarf who beat Loki. He appears in one story, told by Snorri in Skáldskaparmál, but it is one of the best-known in the mythology (see The treasures of the gods: Sif's hair and Brokkr's wager).
The wager
Loki has cut off Sif's hair and has had Ívaldi's sons make replacements, along with a ship and a spear. Then he bets his head with Brokkr that Brokkr's brother — Sindri in Brodeur's translation, Eitri in most modern ones — cannot make three treasures as good Skáldskaparmál 35.
The brother works the forge and Brokkr works the bellows. Each time the smith puts metal in the fire, he tells Brokkr not to stop blowing, and each time a fly lands on Brokkr and stings him: on the hand, then on the neck, then between the eyes so that blood runs into them. The text never says the fly is Loki, but the point is clear. Brokkr keeps blowing through the first two stings. At the third he lifts a hand for a moment to sweep the fly away, and the bellows fall flat Skáldskaparmál 35. Out of the forge come a golden-bristled boar, the ring Draupnir, and a hammer — Mjöllnir, with its handle a little short.
The judgement and the stitching
Brokkr takes the treasures to Ásgard. Odin, Thor and Freyr judge them, and the hammer is ruled the best of all, "the greatest defence against the Rime-Giants". Brokkr has won. Loki runs off in his shoes that cross air and water; Thor catches him. Loki then argues that Brokkr may have his head "but not the neck", so he cannot cut it off. Brokkr settles for sewing Loki's lips together with a thong, using his brother's awl. Loki tears the thong out, and Snorri gives even the thong a name, Vartari Skáldskaparmál 35.
Nothing else is told of Brokkr in the hosted texts.
In the sources
Quoted from the hosted translations; each line is checked against the text when the site is built. Select a reference to read it in context.
Then Loki wagered his head with the dwarf called Brokkr that Brokkr's brother Sindri could not make three other precious things equal in virtue to these.
Straightway the fly settled between Brokkr's eyes and stung his eyelid
Loki said that he might have the head, but not the neck.
He stitched the lips together, and Loki ripped the thong out of the edges.
In modern culture
Not from the medieval sources.
Brokkr appears as Brok, a foul-mouthed blue-skinned smith, in the God of War games (2018 onward), working beside his brother Sindri.