Alignment as a World View (DMG)

In addition to all its other uses, alignment can become the central focus of a campaign. Is the world caught in an unending struggle between the forces of good and evil, law and chaos? The answer affects how the campaign world is created, how the campaign is run, and how adventures are constructed. It also affects players' perspectives on and reactions to various situations and events.
In a typical campaign, the primary conflict in the world is not a struggle between alignments. The campaign world is one in which passion, desire, coincidence, intrigue, and even virtue create events and situations. Things happen for many of the same reasons as in the real world. For this reason, it may be easier to create adventures for this type of campaign. Adventure variety and excitement depend on the DM's sense of drama and his ability as a storyteller. Occasionally player characters discover a grand and hideous plot, but such things are isolated affairs, not part of an overall scheme.
However, for conspiracy-conscious DMs, a different world view might be more suitable, one where the powers of alignment (gods, cults, kingdoms, elemental forces) are actively struggling against each other. the player characters and NPCs may be agents of this struggle. Sometimes, they are aware of their role. At other times, they have no idea of their purpose in the grand scheme of things.
Even rarer are those campaigns where the player characters represent a third force in the battle, ignored or forgotten by the others. In such a world, the actions of adventurers can have surprising effects.
==Alignments in Conflict==
There are advantages and disadvantages to building a campaign around alignment struggles. On the plus side, players always have a goal, even if they're not always aware of it. This goal is useful when constructing adventures. It motivates player characters and provides a continuing storyline; it ensures that characters always have something to do ("Restore the balance of Law, loyal followers!"). Also, a sense of heroism permeates the game. Players know that their characters are doing something important, something that has an effect on the history of the campaign world.
There are disadvantages to this approach, too, but none that can't be avoided by a clever DM. First is the question of boredom. If every adventure revolves around maintaining balance or crusading for the cause, players might get tired of the whole thing.
The solution is simply to make sure adventures are varied in goal and theme. Sometimes characters strive in the name of the great cause. Other times they adventure for their own benefit. Not every battle needs to be a titanic struggle of good vs. evil or light vs. darkness.
Another concern is that everything the characters do may affect their quest. An aligned game universe is one of massive and intricate cause-and-effect chains. If X happens over here, then Y must happen over there. Most adventures must be woven into the thread of the storyline, even those that don't seem to be a part of it.
This is in direct conflict with the need for variety, and the DM must do some careful juggling. A big quest is easy to work into the story, but what happens when the player characters take some time off to go on their own adventure? Are they needed just then? What happens in their absence? How do they get back on track? What happens when someone discovers something no one was meant to know? For these problems there are no easy answers. A creative DM will never be idle with this sort of campaign.
Finally, there is the problem of success and failure. An aligned universe tends to create an epic adventure. Player characters become involved in earthshaking events and deal with cosmic beings. Being at the center of the game, player characters assume great importance (if they don't, they will quickly get bored). This is standard stuff in sword-and-sorcery fiction, so it is natural that it also appears in a sword-and-sorcery role-playing adventure.
Fiction writers have an advantage DMs do not, however—they can end the story and never return to it. At the end of the book, the good guys win, the world is set right, and the covers are closed. The writer never has to worry about it again, unless he wants to. What happens when characters win the final conflict, the battle that puts all to right? What can be done after peace and harmony come to the universe?
Further, the author knows who is going to win. He starts by knowing the good guys will triumph. There may be many twists, but eventually the heroes come out on top. Many DMs make the same assumption. They are wrong.
Never simply assume that the characters will win. What if they don't? What if the forces of darkness and evil win the final battle? No matter how high the odds are stacked in their favor, there is always a chance that the characters will do something so stupid or unlucky that they lose. Victory cannot be guaranteed. If it is, players will quickly sense this and take advantage of it.
==Never-Ending Conflict==
The best way to avoid the problems described above is to design the characters' struggle so it is never-ending. At the very least, the conflict is one that lasts for millennia—well beyond the lifetimes of the player characters.
However, to keep the players from feeling frustrated, certain they can never accomplish anything, their characters must be able to undertake sizable tasks and win significant victories. Player characters fighting for the cause of good may eventually drive back the growing influence of the chief villain, but they defeat only a symptom, not the disease itself.
There always can be a new threat. Perhaps the evil villain himself returns in a new and more hideous manifestation. The DM must be prepared with a series of fantastic yet realistic threats. These gradually increase in scope as the characters become more powerful.
Thus, it is possible to build a campaign where the forces of alignment play an active role in things. It is difficult, and there are many hazards, but imagination and planning can overcome the obstacles.