"Be wary, diviner, of touching fate. It is a dangerous brand to grasp - a sword with no handle, which cuts wielder and foe alike."
Essentially, there are two forces in the universe that determine fate: Law and Chaos. In a purely Chaotic world, everything would be in flux - even the ordinary laws of determinism would fail. Prediction of outcomes, even in the short term, would be impossible. In a purely Lawful world, absolutely everything would be predetermined. Fate would be an iron cage which maps out the life of each creature from birth to death. Most worlds are somewhere between these two extremes.
In most worlds, fate is like a loose-spun net made of strands of Law. The gaps between these threads of fate are Chaos, and they represent free will in its entirety. Most people live entirely in the gaps between - their lives never even come close to brushing with a strand of fate, and their destiny is their own to determine. Others, however, may find that the circumstances of their life cause them to brush up against the threads of destiny, or even to intersect them directly.
If something is fated to happen, it is a virtual certainty that it will. The only way to subvert a fated event is to increase the power of Chaos in a world, causing the strands to unravel. Otherwise, it will occur. However, fated events are rarely specific: for example, it may be fated that a man born on the slopes of a mountainside will unite the three kingdoms and form a new empire. But this does not mean that a fate has a specific man in mind - the power of Law will twist causality and cause the events to occur. If one candidate resists particularly strongly against the pull of fate, it may come to pass that another man - also born on a mountainside - represents the "path of least resistance" for the destiny to be fulfilled.
So how much effect does fate have on individuals? The answer is complicated. In the example above, for example, a man born on a mountainside need not unite the nations. If he fights his destiny, someone else will be pulled into to fulfil the pattern. However, if only 3 men were born on a mountainside and have the possible future before them of uniting the kingdoms, then one of those 3 MUST be the one to fulfil the prophecy. In short, one can negotiate with fate, but one cannot escape it.
It is important not to confuse fortune-telling with prophecy. The former tells of what could be; the latter of what must be. If fate is made up of loose-spun but unbreakable strands of Law, the possible futures seen by diviners are like ephemeral reflections of these strands. Fate dictates that certain things WILL happen; furthermore, causality dictates that certain futures are more likely than others. This is what a diviner sees when they look into the future: an image of a world that could be, within the constraints of the great weave.
As long as there is Chaos in the world, however, the diviner cannot determine exactly what outcome will come to pass. As long as free will and random chance exist, no reality is set in stone. The only way to get certain answers is to grasp the threads of fate directly - the rare and treacherous art known as prophecy. But even this will tell you only what is destined to happen; the spaces between fate's strands are impossible to predict.
The Will of Fate
We have established that fate is Lawful; agency is Chaotic. It is important to note that the other two abstract forces of creation - Good and Evil - are theoretically separate from this struggle between Law and Chaos. After all, both Mount Celestia (Lawful Good) and the Nine Hells (Lawful Evil) are equal forces in the multiverse. So what does fate want? How does it decide which events are fated to happen and who will be caught up in the cosmic weave?
There are some worlds where fate spins its own threads with only Law and Chaos to consider and no interference of any kind. In worlds such as this, fate behaves solely as a kind of stabilising force. Whereas the presence of free will and random chance cause the entropy of a world to increase over time, fate's role is to resist this tendency. It maintains the order of things and the laws of cause and effect.
Worlds of "pure" fate are rare, however - most worlds are quite a bit more complicated than this. When we talk about Law, Chaos, Good, and Evil, we are talking about:
- Lawful Neutral
- Chaotic Neutral
- Neutral Good
- Neutral Evil
But these are not the only alignments. What about Lawful Good? What about Chaotic Evil? When these are thrown into the mix, fate becomes quite a bit more complicated. Take, for example, a world in which there are many supernatural forces and religions, and they are mostly Chaotic. However, there is one powerful religion of a Lawful Good god. In a world such as this, most or all of the power of Law stems from a source that is also Good - and as such, the will of fate tends towards Good aims. In this world, fate is the means by which Good seeks to increase its power.
In this hypothetical world, the other forces (whether Neutral, Good or Evil) are agents of Chaos. They rail against the power of fate and seek to subvert it however possible. They do so by working with events that lie outside the skein of fate - those which are not predetermined - and trying to increase the power of Chaos so that fate's pattern is unravelled. So it comes to pass that, through the battle between fate and free will, every world is touched by the endless conflict between Law, Chaos, Good and Evil.