In between the physical world and the divine realms there is a place some call the spirit world. This is a place where unclaimed divine energy seems to pool and morph into a shadow of the emotions that caused that energy to appear. Those emotions in turn become spirits .
When mortals worship animals, objects, places or concepts. That more directed divine energy can pool into stronger spirits.
That landscape of spirits, created by happenstance or directed religion, is called the spirit world and then becomes the center of a religion called animism, the belief that everything is animated and in possession of a soul.
People that are adapt at interacting with the world of the spirit are called shamans and are often employed by animistic communities as representatives of the mortals towards the spirits. Often the spirits in turn also used such mortals as representatives of their wishes. Giving shamans responsibilities and power in both communities.
Shamans and people they take with them on spirit quests tend to enter a trance, traditionally helped by such means as drumming, fasting, sleep deprivation, drugs, and mirror gazing. More modern shamans might employ electronic music, VR environments, implants or might perceive the spirit world permanently with the help of bioengineered senses.
Spirits when viewed in trance can take many forms. From animal guides and totems, to abstract talking objects that symbolize certain emotions, to disembodied voices of lost loved ones screaming orders and profanity. One example of a traditionally often encountered spirit is a malevolent spirit of disease. The shaman is asked by a sick person to help cure the disease. They go into trance to confront the spirit personification of the disease itself, either placating it with offers, gifts or service, or fighting in off.
Whether the sickness spirit caused the disease or was spawned from the desperate emotion of the patient and their loved ones doesn't seem to matter, getting rid of the spirit almost always helps heal the disease in the physical world too.
There are some famous spirits whose stories and legends are told throughout large parts of the galaxy.