Borgstromancy is the act of revealing setting information via game mechanics. So basically any mechanic which says something definitive about the world is Borgstromancy. For example: Ownership is a metaphysical quality of the universe of Creation. It is defined, in most cases, by the loyalty of the Least Gods of the object in question, whose loyalty is earned via normal maintenance of the object (polishing nicks out of swords, swabbing the decks of ships, etc). This is only revealed in mechanics but it says something about the fundamental animism of the setting