Spirits are an incorporeal manifestation of a once living being. It is not fully understood how spirits are formed, only that they have ties to the Aspects, though, unlike the Aspects, possess agendas and morality. Some may be good, some may be evil, but each spirit has a personal goal or agenda it wishes to see fulfilled, usually by the mortals that dwell within Iriliath.
There is no true pantheon of spirits, as most spirits do not stay bound for long, often only around long enough to see a plan come to fruition. But there are a few spirits who seem to be bound to a greater purpose, who seem to stay around far longer than any of the others. These spirits, a power, though weaker than the Aspects, are far stronger than the mundane spirits, and possess names to be called upon for a service or request. But unlike the Aspects, their motives are not altruistic, and may demand greater sacrifices or prices for what is being asked. And the outcome may not be what the petitioner hoped for.
Beckoning a spirit forth is a rather simple task, usually only requiring a small sacrifice or offering at any makeshift altar and calling their name. The spirit will then appear, demanding to know why it has been called. From then, the petitioner can make their demands and/or requests.