The root of the mystery is a legendary spell book, containing the art of long forgotten magics. You found clues about where this book might be. Based on your information, the book is in a hidden library, somewhere deep inside the Roots Forest. The forest is sacred and has fearsome guardians that look like trees, but they can move pretty fast. If they think you are a threat, they will eliminate you.
So be careful and don't cause any damage if it's possible, or suffer the consequences. I think you can deal with one or two guardians, but more of them will be problematic. However, these guardians will only attack if you truly are a villain yourself. Since they act on Mother Nature's orders, they are basically good creatures. Tread fast and with care because the forest is unforgiving to those who seek nothing but chaos and harm to it. Good luck!