I've been wanting to create a setting with a religious/magic system akin to American Gods or Small Gods. Belief as power. I think I've come close to something like that.
In the Seven Realms every ensouled being possesses Mana. That is, mental and emotional energy, in a nutshell. The Cosmos is constituted of Domains, from the universal to the particular. As the sapient mind conceives and perceives of the world Mana is attributed to these Domains. Domains can be of a Conceptual, Personal, Organizational, Material, or Phenomenal nature. Personal Domains in particular are basically one's image in the minds of others. All relationships consist of the mutual or one-sided attribution of Mana towards the Personal Domains of those individuals involved.
Domains can be "dominated" by sapient ensouled entities (humanoids), dead or alive, and materials through association or possession, in which case the "dominators" receive a share of the said Domain's Mana to the degree that they are associated with it or in possession of it.
When Domains receive enough Mana they transform into Real Domains. Real Domains can only be dominated by humanoids, spirits, and materials who's Personal Domains themselves are Real Domains; that is, by Apparitions, Apotheists, and Relics, respectively.
Real Domain dominators possess the ability to influencing, by force of Mana, their Real Domains. They possess the ability to Transform one Real Domain into another, the ability to Conjure their Real Domains out of nothing, and the ability to Configure their Real Domain into any form. This forms the basis of Arcana. Arcana is therefore the Transformation, Conjuration, and Configuration of Real Domains.
Dominators grant humanoids access to the Real Domains they (partly) dominate. Here the Three Orders find the origin of their divergence. Apparitions patronize Templar Orders, granting templars access to their Real Domains. The descendants of Apotheists constitute an alliance of Great Clans called a Subcaste, the knights of these Great Clans possess access to the Real Domains of their Ancestor Apotheists by virtue of their Bloodline. Relics are commonly owned by the adventurers of an Adventurer Hall, granting them access to the Real Domains of their Relic. Each of the Three Orders form a Karmic Oath, a covenant, Karmically enforced, which binds each to their Apparitions, Ancestors, or Relics.
This is the general conception of the system. Please let me know what you think.