In a lot of RPGs, you have the ability to select your character's model and appearance. Generally, this doesn't affect the character's abilities or stats in any way, but does give you the chance to personalize the character and let him stand out in multiplayer. In this game, you have a whole team of such characters that are created by combining body parts. These parts all have inherent stats and characteristics, with the resulting complete hero being literally a sum of its parts.
The head is the most important element. It contains that character's knowledge and personality, so is the default "core" for any new identikit hero. If the head's a wise-cracking joker, so will the resulting hero. The head also contains all the abilities a character knows, but these abilities can only be earned by using the right combination of other body parts. So you can't learn any sword-fighting abilities until you have an arm holding a sword - but once you have learned that ability it'll stay with the head from then on. So you can actually switch a head's body after it learns a lot of fighter skills, for example, to allow it to start learning magic skills instead. Of course, some abilities can't be used without the right body part equipped (you need a sword to use some sword-fighting moves), but most abilities will be available even after changing the body part that you learned the ability from.
The torso is another vital component and comes right after the body's head in the hero creation process. The body defines a large part of that hero's eventual hit point and armor scores. It also provides the lion's share of the character's stats. The arms define the character's profession, since some arms are holding weapons (equipping those allow you to use that weapon and learn abilities associated to them) and others are able to conjure magic using hand gestures. The legs contribute a large part to the character's overall speed and agility. Finally, you also have a "bonus" body part, which can be various additional body parts such as horns or wings or a tail: These are optional (you can make a hero without one) and the character can only equip one at a time. The arms, legs and bonus body parts also contribute to a character's HP and armor, but to a lesser extent than the torso. There's also a weight factor too, where heavy body parts (those that are better armored) will slow down the resulting character's speed. All body parts (besides the head) can have abilities attached to them that you can learn: the arms tend to have most of the martial ones, but the legs can have dodging skills and the bonus parts can have special abilities included as well. You get a bonus for forming a "pure" hero (one where all the body parts match) but these heroes tend to be limiting in the long run: you'll earn more abilities and powers by mix-matching. Don't be afraid to break up your pure fighter if a stronger body part with a useful ability comes along.
The game itself uses these combined heroes as a group to pillage and loot the various locales of the game, in part to discover new body parts which you can use to construct even more powerful units. Gameplay-wise, it'll play like a large-team RPG strategy game, either real-time or turn-based: despite my usual preference of the latter, I think the former might actually work better for this idea. Some body parts are rarer than others and therefore tend to be more powerful. As well as body parts of corresponding RPG classes (armored knights, robe-wearing magicians, forest-gear wearing rangers and so on), you can also find body parts of humanoid monsters which often provide higher stats in some areas. A cat-like humanoid race's legs might be considerably faster than a regular human's, for instance. These humanoid abilities might also have unique abilities of their own (a troll body part might be able to provide the Regeneration ability) for you to learn. Eventually, you'll discover many rare body parts that don't correspond to the vaguely-medieval setting of the game, with anachronistic body templates such as cowboys, ninjas or robots. All of these body parts can be found in either treasure chests or taken from the bodies of your defeated enemies.
Eventually, you'll have a huge number of body parts with which to create a very eclectic-looking bunch of heroes. Experimentation will be the key to find the ideal combination of body parts for any one character and because the heads' personalities are all different, you may find some body parts work better for one head than it does another.
