The setting for my game is a pseudo-medieval France, if Rome had never become Christian, the Moors never left Spain, and the Netherlands were Slavonic. Otherwise, most standard fantasy tropes are at play. A major cataclysm occurred just over four hundred years ago, and about forty years ago was a mark r outbreak of plague, that dramatically reduced the population and left villages, castle and other structures uninhabited. Perfect adventurer bait.
Northport, formerly the Roman colony of Antillarus, and earlier than that Yagratz of the Goblins, has been continuously inhabited by a variety of peoples for something like four thousand years, and most of it underground due to a persistent firedrake problem. Persistent, at least until a Dwarven Sorcerer named Federjung took it into his head to weave a spell to displace a nation of trolls from their mountain in order to access the gold the trolls were mining.
Needless to say, the spell backfired stupendously, and while the trolls were teleported leagues away and beneath Northport, the dragons near that city were whisked to Trellheim. At the same time, there were earthquakes, tidal waves and a hail of meteorites accross the land.
At the time of this thaumaturgical disaster, a wizard named Abarax, who had ascended to a potent state of undeath through necromantic research, was stricken by a near direct hit by an anti-magical meteor deep in his steading beneath the city. Deprived of contact with the magical emmenations that preserved his form, Abarax drifted into a centuries long form, until reawakened in the present day by a powerful stone troll named Leopold.
At the time of the Federjungian incident, Abarax had an apprentice, a wizard named Flax, who managed to survive past the apocalyptic occurrence for some time. He became rather learned, and maintained active correspondence with other survivors who were magically talented.
Enter a wealthy Sage to modern Northport, obsessed with the incident and following a lead to track down the lost library of Flax the Necromancer, and direction is found for the most active players in the game. Other groups are fighting trolls below the winecellars of an ancient manse, helping a fight organizing ogre rebuild his gambling empire, or pursuing a diabolical cult into the ruins below the city streets.