Smog Spirit

Smog Spirits are monstrous flying creatures, beasts of smog and poison who manifest from nothingness and carry their victims away in the night. They kill, corrupt, and abduct - often targeting Windweavers.
Little else is known of these elusive beasts. The Gods found and slew one, and discovered that the essence of the spirit is tied to a small piece of hardened wood inside of it - the rest of the spirit is amorphous and can easily regenerate if allowed to. 
What they want and who they answer to is unknown.