Spirits in Werewolf serve both as a great resource and a great problem. They are the primary inhabitants of the Shadow/Umbra/Ether, the reality that exists on the other side of the Gauntlet. The Gauntlet is the barrier erected to prevent “normal” from directly interacting with “abnormal”. Many werewolves and other supernaturals have the ability to pass through the gauntlet into the lands of spirits. Most spirits do not welcome the intruders and many will actively oppose the unwelcome guests.
However, spirits provide much benefit to werewolves. They can be consumed to help in healing and regaining power, they can provide other-wise unknowable information, they can be powerful allies and they can mean the difference in winning/losing/surviving a fight.
Spirits come in all sizes, shapes, mentalities, personas and types. Everything that has ever been created, everything that has ever been felt, everything that has ever occurred has a spirit associated with it, but not all spirits are awake or active. A grain of gunpowder’s spirit is so miniscule as to be effectively irrelevant, but a bullet or pistol could have a very powerful spirit. For example, Captain Jack Sparrow’s pistol with one shot in it probably has a very powerful “revenge” spirit awake within it – thus the perfect shot at the end of the movie to defeat Captain Barbosa.
As I stated, spirits have their own agenda’s, often opposed or irrelevant to the werewolf’s. This means that when you try to contact one, you must approach with caution and understand the actions of the spirit may make no logical sense.