What if some crazy wizard created an artifact that empowered rodents that touched it with one random supernatural power? Preferly right out of the pages of your favorite four-color. (But only one power!) This item does not convey any sort of intelligence boost.
Somewhere along the line, someone very powerful lost their marbles. Literally. Possessing a marble allows incredible clarity of thought about a particular related subject.
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.