Sylvae (2003)

Translated from the Publisher's Blurb:

In this game, the PCs play trees. The setting, the forest, is the home to an ancient fratricidal struggle between the magician and his evil sister, the black fairy. In addition to their participation in this war, alongside the lovely surroundings, the trees also coexist with other peoples of the forest, elves, satyrs, fairies, animals and plants too, and may be faced with the Exterior. The tools of the PCs are their great strength, the strange magic of Dreams, Clouds, and the support of their relations in other nations.