Why FOG as a nemesis?

"The bitter fog blew into our Meeting Lodge and threw papers, chairs, and pictures around. Then it blew into our School House, knocking over our desks and chairs. Our books and paper flew everywhere. The fog slowly crawled through the lower yard, then disappeared into the PortHold. I thought this must be death. But for whom, we, the Elfin folk nor Faeries die; we are ageless. Maybe the Trolls die?"

Reasoned, Barren Flynn, the Elfin Prince of the OakGrove gardens as this fractured tale begins...