I REALLY like this theory. Is there any way I can upvote it or otherwise officially approve it?I'm working on the world first and worry about adapting specific game systems to it later. Though I don't think there's actually that much that would need adapting. Character races, equipment lists, and some new monsters should be covering almost everything. The only really setting unique things that come to my mind are mechanics for demonic corruption and a kind of blood magic, which I havn't really developed yet.
Magic and Spellcasters
In the world of the Ancient Lands, there is only a single supernatural force at work. Life force, magic, spirits, demons, souls; it's all the same basic energy that is found inside and between everything. This energy is what gives living creatures their strength and make them grow and heal injuries and disease. It is also what creates the souls of mortal creatures and in places where the energies of the landscape are strong, they manifest in sentient spirits of imense power.
The arts of magic are the mastery of the ability to not just call on the life energy within oneself, but to extend ones mental control to the energies around one and even inside other objects and beings. When casting a spell, a spellcaster is sending a ripple through the energies surrounding him to manipulate the energies within creatures and objects to their desire, just as normal people control the energies within their arms and legs. Magic spells can make plants grow or move, split or shove away rocks, create lightning and set things on fire, and even take control of other creatures thoughts. To be able to manipulate the life force and magical energies at a distance, a spellcaster needs to build up a reserve of energy separate from their own life force, which they accomplish by many years of training and meditation. Once this reserve is spend, they can no longer cast any spells until the energies are restored. People who have mastered magic, and creatures that are naturally magical, require almost no effort to regain their spend magical energy. Their energy reserve has become a natural part of their own being and during rest energies from the surrounding environment automatically move in to fill the void and restore the natural balance of energies, like water after a bucket has been filled from a lake. Compared to the amounts of energy in the natural world, even the most powerful spellcasters can store only such a small amount that there is no noticable drain of life force in the creatures and plants arround them.