A spirit can be defined as an incorporeal being believed to have powers to affect the course of human events and can become visible (or audible) to human beings.
The spirits that players encounter in the game can be considered as spiritual beings (concerned with sacred matters or religion, affecting the spirit or the soul), supernatural beings (forces, beings, and events that are beyond what can be explained by nature), and cryptids (entities from the folklore record and whose existence or survival to the present day is debated).