Ok, so we now have a theme, the scope, and we know about the resources and that the world has. Now we need to look at something important to any fantasy world: conflict.
In order for any hero to emerge, there must be conflict, because, in a perfect world, that hero and their friends would not be needed. The conflict can be immediate (and often is, especially when centered around individual adventures) such as a war, a catastrophe about to happen (aboleths summoning meteors), or inevitable (like Golarion's unexplained loss of Aroden, and the sudden failure of prophecy, where before it was reliable to a fault). The one thing to remember is that the less immediate the threat it, the less important it will feel to the heroes. Again, to use Golarion as an example, every hero knows that Aroden died, but they barely worry about it, as they're busy keeping up with things like the Runelords trying to take over the world. There could (and most often are) multiple levels of conflict, that the heroes can encounter, ranging from village-level (bandit raids) to world-threatening (dragon council conquerors), but you need to set the MAIN conflict front and center for your world and your mind as you create for the world.
Here, in our little world, we've already established that there'll be a war. But even there, there is some leeway in what we want: It is ongoing? Upcoming? Can it be averted if so? Has it just passed, or is it a Cold War? There might even be a stalemate. For now, we're going with an uneasy stalemate, but not a truce. For the heroes, it means that the war is immediate, and while it's not flaring up at the moment, it could at any time - perhaps the heroes can affect it towards outright war or peace with their actions.
After this, it's time to think about what has led up to the current conflict. Of course, this depends mostly on what sort of conflict it is that your world is seeing, but it bears thinking on, as it'll help set the tone for any adventures and campaigns you put into that world.
When thinking about it, consider if the cause for the conflict is well-known, or if it was hidden. If it’s the well-known cause, was it ACTUALLY that one? If it was hidden, how was that done, and by whom? And what happens if that conflict breaks out into the open — more importantly, what are the consequences of it doing so?
In the world we’re building here, the conflict is well-known. The two sides have been at war for a couple of years, and have built up quite the animosity against each other. But, they recognize that the war has been hell on both sides, and a stalemate has been reached, where they are marshaling their forces currently. Neither side wants to meet for negotiations, but neither are they trying to push each other around. They’re still from the same nation, and anyone below the nobility knows that this is the case (and remembers it), and has family on both sides of the conflict.
And the cause? A single man, who wanted to overturn the government and take control of a new nation under his control. He’s spent years fomenting trouble at the upper levels of society, playing the various noble houses against each other, and getting the schools of magic to support them. Traditionally, the eldest child of each noble family was given control of the family, while the second eldest was sent to a magical academy for training, resulting in that all prepared casters (wizards, etc.) having some noble blood in their line.
He was killed within the first two weeks of fighting, as he thought he was a great general, though it turned out that he was in fact, incompetent on the battlefield. This caused the war to rage for three years, only just ending now. Both sides have done things they shouldn’t have, and both sides blame the other for taking the first shot.
And we’ll return to our world next time. 😊