King Iorek Byrnison is a male armored bear (panserbjørner in Norwegian). Like all Panserbjørner, Iorek follows a very strict code of conduct, and will not, in any situation, betray a promise he has made. He possesses incredible strength, and like many of his kind is an expert smith. He is a great friend and comrade to both Lyra Belacqua and Lee Scoresby.
During the first book of the His Dark Materials trilogy, Northern Lights, Iorek Byrnison is found shaping metal for humans in an Arctic port town. These humans had deceived Iorek by giving him spirits, then stole his sky-iron armour while he was intoxicated: this left him no choice but to work for the humans. He tells Lyra Belacqua that if he had his armour, he would kill the humans that stole it, but that without it he would simply be gunned down attempting to get it back. Upon hearing this, Lyra decides to use her alethiometer to find the location of his armour, so that he can break free and join her quest.
Using the Alethiometer, Lyra discovers that the humans have his armour hidden in the cellar of the local priest's house. Almost immediately upon hearing this, Iorek rushes off to find his armour, waiting only to finish his work hours. The humans, suddenly realizing his intent, try to kill him; Iorek is about to crush one of the attackers' heads when Lyra convinces him that it would be better not to hurt the man, as this would lead to more fighting and delay their voyage.
Later, Pullman reveals that by bloodline, Iorek would have become King of the bears in his homeland, Svalbard, had it not been for his exile. This exile was mainly the fault of Iofur Raknison, Iorek's successor as King, who was suspected, but never explicitly proven to have used drugs on another bear in order to make him act unusually. This befuddled bear went up against Iorek Byrnison in a ritual of dominance to win over a female bear. In his drugged state, however, the bear went against normal procedures and would not back down when any bear would normally have done so. This situation ended in Iorek killing the bear, which condemned him to exile. When he returns to Svalbard, Iorek fights and kills Iofur Raknison, reclaiming his rightful place.
Later, he is forced to take his bears on a voyage down to the Himalayas because the climate in his home country of Svalbard has become inhospitable due to Lord Asriel's unintentional changing of the climate by opening a rift between two worlds. He later demonstrates his skill as a smith, repairing the Subtle Knife - including its magical properties - with no specialist equipment and only the aid of Lyra and Will. He and a regiment of his subjects fight on Lord Asriel's side in the battle on the plains; as part of this he takes Lyra and Will to find their lost dæmons. At the end of the Amber Spyglass, it is revealed that he returns to Svalbard and reigns as king of the bears.
In the film he is voiced by Ian McKellen. He has also been portrayed on stage by young actors Sandy Howie and Stuart Leel in the Scottish Premiere of the His Dark Materials stage show by the Scottish Youth Theatre. In the unabridged audiobooks, Iorek is voiced by Sean Barrett.
Read more about this topic: List Of His Dark Materials Characters, Main Characters