Spirits usually value good stone work, naturally smooth stones, and exotic gems over gold or silver. Although the exception is made for specific types of coins or sculptures made specifically for a spirit or spirit god. Usually. They also value such things as wood carvings, bits of bone or blood, and teeth. Some of the more evil spirits crave sacrifice and death.
Hood Episode One
Dark spirits and demons fear the grinning Jack-o-Lantern. Certain artifacts of unknown origin, such as the rune-covered hammer found in Cameron's room, can be used to communicate with some shades and demons.
Hood Episode Two
The spirits and demons that haunt the woods around Shadetale are not all-powerful. CourSid creates a potion for Cameron's father that successfully hides his presence from those native shades. Only CourSid could tell us if it is magic or science. The other Bundled that live in the swamp clearly have their own secret ways as well.
The demons of the forest fear other things apart from grinning Jack-o-Lanterns. According to Boyen the Shaman, they are afraid of the ancient technology from beneath the swamp.
Not all of the entities in the forest are malevolent. Some, like the one-horned orange spirit who points out the water, are helpful. Others are eager to make deals, be it for 'candy' or the invaluable runed hammer.
Hood Episode Four
Shades, demons, and spirits reside primarily in Gorsus, or the Spirit World.
In order to possess a person, a demon requires a contract with that person. Except for the Archdemon who spirited away Cameron. This entity somehow has the ability to influence reality even from the confines of Gorsus and without a contract.
The Hunter encounters a happy little fire spirit in the Spirit World. Apparently, they love sapphires.
The Hungry Demon tells the Hunter that spirits and demons cannot hear the songs of birds.
The Hunter releases a thousand fiends in order to open the way to the Archdemon. Fiends have not been seen in the world in thousands of years, and apparently they are very bad indeed. The Hunter made this difficult choice, however, because he says fiends can be recaptured, but an Archdemon cannot.