Genesis is the first MMORPG-esque game where players can actually play as creatures in the game. In fact, there are absolutely no NPCs or creatures controlled by artificial intelligence (with the minor possible exception of small fish and game, and livestock). Creatures cannot equip items or armor, but they do have the unique ability to evolve. You choose a base type of creature and evolve different traits like tougher hides, the ability to breathe fire, chameleon-like abilities, and so forth. Beasts can be limbless, bipedal, quadrapedal, sexpedal, or octapedal (and can evolve fins or tentacles in place of feet), and they can evolve traits that will allow them to fly or swim. Beasts can evolve from various basic forms including insects, mollusks, fish, amphibians, reptiles, mammals, and birds. I may or may not include the ability to compose chimeras (beasts of mixed parts), and the same goes for multi-headed beasts like a hydra or manticore. I know it could be disappointing if this feature isn't included; like you, I also really wanted to play as a three-headed platypus. Essentially, the evolving system will work in a similar manner to Will Wright's Spore, although it won't be as detailed, but rather stripped-down to the most necessary components. If you think I am copying Will Wright, you haven't played Evo for the Super Nintendo. Beasts are elementally aligned, and their alignment determines the range of features that they can evolve (for example, a beast aligned with the Fire element could evolve the ability to breathe fire, but a beast aligned with the Poison could only spit acid or breathe out a noxious cloud.)
You might be wondering who would want to play as a rat, if the possibility to play as a dragon existed. Again, this is where evolving comes in to play. In order to become a dragon, you must first start out as a lizard, and eventually evolve the features, size, and strength to become one. Many traditional mythological beasts can be created through the evolving system. For example, a bird of the fire alignment could evolve to a Phoenix-like beast, or a mollusk of the water alignment could evolve to a kraken. In fact, the system will recognize your evolved features and attempt to classify you as a particular beast (mythological or not).
One very interesting feature in Genesis is the mounting system. When humanoid players mount a beast, the beast controls the movement, and can attack others independently of the humanoid. When the player tries to move, it merely gives the beast directions (arrows point in the direction the humanoid wants the beast to move, which the beast can choose to ignore if it wants). However, players can attack from the beasts back in any direction they want. Mounting gives players protection, while it gives beasts extra fire power. Many beasts are likely not to perform their services for free, however…players must feed them sufficiently to keep them around. There may even be a taming system implemented, but whether this will be included is not certain yet.