Before the county of Corvis, there was the Wizard Corvus. Thirteen hundred years ago, a mad powerful wizard had an estate in the area that became the county of Corvis. Over his 800 year span, he created thousands of magikal items of various types and power level, some of which survive to this day.
After particularly intense storm, a green glowing fungi can be found on the trees and plants. Also new monsters seem to be in the region. These storm are obviously bringing these things from other places and depositing them with the wind, rain, and goop upon the land.