Legend of the Four Blades
The spirit world is a world that overlaps the physical. With one exception. mountain or river in the physical world could appear vastly different. A single mountain in the physical world that possesses a powerful spirit inhabiting the mountain could appear grand and golden, teeming with precious stone. A river could be grand and flowing with water much like free-flowing sapphire. Of course the spirit world can also be indirectly, or directly influenced by the actions in the physical world. Places that have seen the blood of battle may be dark sinkholes of evil where evil spirits roam. The sight of a sacred temple could be a golden land of prosperity which in turn rubs off on those visiting as a sense of ease or dread. Beware such sinkholes for what eminates evil and good attracts evil and good as well.
Likewise the spirit world can be reached through various means. The ‘Astral Projection’ spell instead sends one into the spirit realm a place where one could directly commune with ones ancestors for wisdom, clear blighted lands from the source, though beware as the spirit world has its own threats and dangers in the form of spirits, oni, and dreaded Onryo.