Axioma
When was the last war fought in your world, and why?
I'm going to go with my fantasy world for this one, because I find it the most interesting in this regard, as there are actually several on-going wars, depending on what area you're looking at.
In the South Lands, there's the trolls (which are nothing at all like the standard D&D trolls) and the various human kingdoms that are collectively known as the Inkai He-ged, who are allied in their fight against the Ming Srak, which are basically magical servants created through a joint effort by Serak Nell (the now dead goddess of chaos) and Mingen Raul (the now dead god of magic). The Ming Srak were never intended to be anything but temporary creations, but because of the nature of their creators (especially Serak Nell), they managed to overcome that restriction on their existence. Which wouldn't have become a problem if they didn't also multiply. They were almost wiped out during the last war among the gods (when they were created), but discovered they could take refuge in the Heat Wastes, an area that the god's war had corrupted so extensively that no more mortal races could survive there, and so survive. Except there was nothing there for them to occupy themselves with, and being the offspring of the chaos goddess, they went searching for something to do.
Because of this conflict, the Inkai He-ged and the trolls have intertwined culturally for mutual survival against the Ming Srak, and their use of magic is far more advanced than that of any other human culture. Despite this, the Ming Srak are slowly but surely beating them down, and have recently snuck around to the eastern side of the continent, where they've encountered the thriving half of Sjal Shkrack, the "unifying" empire of the humans.
They've met with little resistance here, but have encountered the shamans, which are undead somewhat akin to liches and that serve the rulers of the empire. Unlike liches, shamans can not be killed, as their physical form is only a manifestation of their true existence in a mirror universe. Being creatures of magic, they, like the Ming Srak, are adept with its use, and the clashes between the two races have already sprouted several legends.
Which isn't to say the shamans are beneficial. They're not. Everytime their physical form is killed, it drives them that much closer to madness, and many of the older ones are completely insane and utterly dangerous. The empire's reliance on them is thus a double-edged sword, but at the same time, they are the only source of powerful magic that the empire has, as the humans of the North Lands are extremely wary of it, given the still lingering scars of the god's last war.
In a way, they're fear is justified, but at the same time, they're also dooming themselves, as without it they have no effective way of dealing with the shamans who pass the brink of madness, have no way of dealing with the Ming Srak, have no way of dealing with the followers of the god of insanity (even if he is dead), and have no way of dealing with the Banda Korronn (a race of elves cursed to forever be that which they most hate: undead).
Which brings us to the western half of the Sjal Shkrack empire, which is crumbling under it's own weight and lack of resources. The Banda Korronn, having been searching ceaselessly for a cure to their condition since it was inflicted upon them, have lost sight of the goals they had at the time of their curse (a few thousand years passed will do that), and now have no real understanding of why they were cursed in the first place. They've lost none of their zeal, however, and under the leadership of Eldroh Rillyhre, have taken to conquest, looking for a power beyond that which they've managed to find for themselves. Already, they've made short work of the human nation of Seltora and have discovered remnant powers of the world's first gods, but they have no understanding of how to use them, let alone get to them. They're now poised to strike outward, at Sjal Shkrack and the Edrrin Gra'Yur, who were once their blood kin but escaped being cursed.
There are also further wars on the horizon between the now displaced High Druids (an actual race that I haven't yet gotten around to renaming) and the shamans of Sjal Shkrack, a conflict which is likely to completely destroy the empire, as the High Druids are one of the very few (and dwindling) races whose existence is founded upon magic. Being nigh immortal, their power is not to be taken lightly, but having lost the only home they had to a focused onslaught by the followers of the god of insanity, they are now scattered across the realm, and thus weakened.
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If there's magic in your world, how prevalent is it and how does it affect the cultures and societies of your characters?