From publisher blurb:
Warriors of the Wild is a fantasy d20 product line designed for both players and game masters. It offers well-balanced and thoroughly play-tested classes constructed around various animal, natural, and tribal themes. These classes are perfect for any combat-heavy game, be it in dungeons, cities, the wilderness, or other planes.
This product features the force of nature, a prestige class ideal for barbarians and fighters, but also suitable for other martial characters. Able to grow in size and regularly gaining ability boosts, the force of nature is a behemoth of raw power. His stone-hard fists are the only weapons he needs to pummel opponents to death.