Choose your creature (or go as yourself), grab a weapon, and go destroy your enemies. You can team up with other players to do some zombie hunting, or you can go against the players themselves.
Please note that while the creature form you take has no affect on your abilities, each has more obvious advantages and disadvantages. The tiny black spider is good at sneaking up from behind, many of the animals are good at blending into the forest regions, and the dragons are just plain cool and intimidating. So choose your form and weapon wisely!