I imagine him as a nearly feral Chaotic Neutral character whose Dog sidekick (NEVER a mount!) is his closest friend. He was found in the wild as a youth, after an unnatural storm took his family from him. Whatever caused that storm left its mark on young Vanir, who has gained an intuitive grasp of the arcana of storms and air elementals. Being so charismatic, Vanir makes friendly acquaintances easily, though his storm-driven temper makes him a dangerous foe.
Vanir only recently came into his sorcerous birthright (typical "18th Birthday" type thing), and he adventures to push the limits of his powers and discover what his true limitations are.
Here's his Summary data. It's not as nice as the HeroLab Pathfinder data, but it will give you the idea.