Bromine Lake is a lake that is almost a very small inland sea. It is also special for other reasons. It always has the warmth of a living Human, no matter what the season. It is not a hot spring with its sulfuric chemicals. There are hundreds of theories, but no answers.
Even if they did, they would never believe it, as it has ties to the time of legends, to the time of Corvus.
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.