A Compendium of Creatures, Magic, and Spells from the Forest
From the introduction:
The Book of Forests is designed for Dungeon Masters (DMs) who desire to extend their campaigns under the eaves of mighty and ancient forests.
Herein you will find a variety of creatures, both goodly and foul, that grace the forests of the fantasy world. Many of these have special connections to elves and elven communities, while others represent malevolent manifestations of trees. The creatures are of a variety of challenge ratings, though they tend to skew towards being adequate challenges for low- to mid- level PCs.
In addition to a large number of new creatures, this book contains just over a dozen magic items that relate to elves or the forest. Many of these items can only be utilized by elves, half-elves, or druids.
Finally, six spells are presented that relate to nature and forests.