The Panserbjørne are the armoured bears of Svalbard in Lyra's world. These armoured polar bears are capable of intellectual processes and communication (at least) at par with other conscious beings in the many worlds of His Dark Materials such as humans and mulefa. They are famous for being impossible to deceive. Their great knowledge of metallurgy and the opposable thumbs (described as having hands like men) on their forepaws make them exceptionally skilled metalsmiths, far beyond the ability of humans.
They forge their own armour, which they regard as comparable to their "souls" although it is made clear that the bears do not regard themselves to have souls as humans might. The panserbjørne make their armour from sky iron or metal collected from meteorites. The rarity of the metal and act of forging oneself one's armour likely contributes for the strong relationship between bear and armour.
|"It was rust red and crudely riveted together: great sheets and plates of dented discolored metal that scraped and screeched as they rode over one another. The helmet was pointed like his muzzle, with slits for eyes, and it left the lower part of his jaw bare for tearing and biting."|
|Philip Pullman, The Golden Compass (Knopf 199)|
The armoured bears of Svalbard are ruled over by a king, determined by bloodline.
After the rift in the sky is opened up by Lord Asriel at the end of Book I, many worlds encounter some sort of climate change, including Lyra's world. The bears find Svalbard to be inhospitable as the ice melts and their usual food sources dwindle. They are thus forced to leave the centre of their civilisation for a new home. Book III finds the armoured bears on their way to the Himalayas.
The word panserbjørne is plural, while panserbjørn is singular. It is derived from the Danish words for armoured bear, where panser means armour and bjørn means bear.