The One Who Came with the Fog

My first memory is of fog teeming with monsters. I don't remember who I am or how I got here, but for some strange reason, the monsters don't touch me. Learning that I came with the fog, some wish to burn me as a witch, while others protect me. The king's advisor even sends me as a spy to the Nergard castle to keep an eye on the sorcerer he dislikes. At first, he seems quite nice. But they all hide something, and I will have to figure out who the good guys are, who the bad ones are, how they are connected, what I have to do with it, and why I immediately fell out of favor with the head of the Nergard guard. Only one casual acquaintance is definitely on my side, even though he doesn't know me at all.