Once, there was a world where the Powers had an active hand in guiding humanity.
The Power of Agriculture helped the farmers with their livestock and crops. The Power of the Hunt helped hunters and trappers find meat and fur, and helped keep the predators at bay. The Power of Wisdom guided kings and advisors, while the Power of Justice guided divine knighthoods dedicated to her beliefs. The Power of War granted strength to all who heeded his teachings, and the Power of Death guided lost souls to their final destination.
All this changed when the Powers disappeared.
It happened so quickly that even the divine servants, the archons and devils, devas and demons, had no idea what happened. They quickly blamed each other, and fell upon another in a futile act of revenge. When they died, they disappeared, never to return.
Meanwhile, the mortal races found themselves lost and confused. They had become so dependent on the deities being a part of their lives that they didn’t know what to do or how to act in their absence. Crops grew wild, predators began harassing villages. Kings acted on their own mortal judgment. Once noble knighthoods, without divine guidance, began to deteriorate, becoming something else entirely.
All was not lost for the mortals, though. In the wake of the disappearances, people began to see a commonality in their dreams. A world, overlying their own, that many could visit as they slept. A common dreamworld, with spirits that embodied ideas and aspects of the mortal world. As time progressed, people found themselves with new companions: spirits that had decided, for one reason or another, to attach themselves to the person in question. Sometimes the spirits granted the host permanent boons; sometimes, it empowered the host to create blessings and curses, spells and constructs. It depended much on the combined nature of the person and the spirit.
In time, a few mortals were able to enhance their connection to the dreamworld, drawing more spirits to themselves and turning imagined constructs of power into reality with greater ease. Their greater connection came at a cost; the person would begin to change, physically and mentally, as they gave more of themselves to the dreamworld.
A person can be strong in body and weak in the dream, but some of his strength can carry over, depending on his attunement to the dream. A mage might create a spell in the dream, and use his attunement to make the spell manifest in the physical. A thief might choose to let the spirit of stealth he has attracted to act through him, granting him greater skill in hiding as the spirit bends shadows around him.