The look of the belker has changed from 3.5 to Pathfinder—the former was droopy-faced and demonic, the latter more like a smoky, insectile bat—but the essentials are the same. They are hateful beasts of smoke, an edgy alternative to the usual air elemental.
Talidar is a prosperous city, whose gleaming, high-walled streets look out over a glittering azure sea and a harbor full of eager tradesmen. But if the walls and towers are freshly whitewashed, it is by necessity. Talidar is home to a sprawling university for mages, whose many rival colleges might as well be feuding social clubs. Talidar’s wizards and summoners are unique in that all are taught to bind small belkers, whose size then grows with the wizards’ power. Dueling by belker is the norm, and the sooty trails left in their wake (along with the occasional fireball char) keep the rest of Talidar’s citizens scrubbing furiously but saying little.
Earthquakes cause a pocket of gas to rupture up into the market square. In addition to the threat of poisonous fumes, a pair of belkers menaces all who come near.
A janni’s human husband is found dead of smoke inhalation and internal injuries. A belker is the likely culprit, but did it act alone or under the compulsion of some other foe?
—Pathfinder Bestiary 2 45