The Great Chain of Being connects everything that exists in a just hierarchy of responsibilities. However, in practical day to day life, you don’t really need to invoke the Great Chain itself. That’s overkill.
The Great Chain has a number of subsidiary incarnations, lesser reflections of Heaven’s will that govern most encounters. For example, filial piety governs the relationship between children and their parents. Loyalty governs the relationship between vassals and their lord. Respect governs the relationship between teacher and student.
Even more specifically, local fetters of the Great Chain bind people and spirits together in a much more personal or individual fashion. This woman is not just a parent but YOUR MOTHER. This spirit is not merely a local god but TIGER TIGER, the embodiment of the land your home village is dependent on for survival.
So, while the Great Chain connects everything, some connections are much closer than others and offer much more immediate leverage. If you invoke the Great Chain of Being, Heaven will get around to resolving the problem eventually, but it may take several hundred years and could involve wiping everyone out so there’s no longer any problem or record of the problem.
However, if you invoke a more specific fetter, either a general relationship (a shaman’s duty to intervene between people and spirits) or a very specific one (this shaman is YOUR SHAMAN, with a personal duty to you), the results will be much quicker and coming, either in providing you leverage to demand that someone else do (or not do) something, or in creating negative consequences for them spurning your just demand.
On the GMs side, then, the Great Chain and its fetters serve as guidelines for determining what happens next. You know how, in Dogs in the Vineyard, town creation is a process of following the pride or sin and seeing how it develops through the world? That’s what GMing a game of Ghost Opera is like. When characters and NPCs do things, you simply follow how these actions affects the Great Chain and its more specific fetters, which is easy to do since you and the players are going to be invoking the Chain all the damn time. And then you generate new situations based on the ripples created in the Chain.
For example, if a character demands that their village shaman intervene in the spirit world… and the shaman refuses, that creates unresolved tension — injustice, from the perspective of the Great Chain — between the shaman and their village. There’s also spillover affects, since injustice in inter-village relations (or any other relations) invokes responses from the natural and spirit worlds. And the rules will then provide the GM an opportunity to have more bad things happen to both the shaman specifically and the village as a whole.
Sure, the shaman can keep defying the Great Chain and its fetters… but not indefinitely. Eventually the social, natural, and spirit worlds will build up such a huge array of forces against him that the shaman will surely be crushed, either killed outright or violently diminished. However, the Great Chain is both patient and inexact in handing out justice. The personal problems of the world are “like straw dogs,” totally immaterial. If it takes several years and involves massive amounts of suffering by people and spirits, Heaven doesn’t really care. Heaven is not compassionate; it simply dispenses justice on a macro scale. The fallout comes down all around, punishing both the shaman and the people and spirits that allowed his folly and arrogance to continue unchecked.
It is generally in the interests of people and spirits, then, to resolve injustice before Heaven does. The Great Chain exists not simply to punish or restrict them, but to guide them towards righteous behavior and make it perfectly clear where injustice is. The Great Chain is very noisy. When you push against it, it makes a loud metal jangling, which eventually carries up the Chain to greater powers: lords, local spirits, and, eventually, the ancestors, the dragons, the king himself, the high god Di, and Heaven itself. In fact, now that I think about it, Heaven doesn’t really even need to intervene itself. Before that, storm spirits, wild animals, soldiers, monsters, dragons, and the like will have solved the issue for it.