Dark Obelisk 1:
Berinncorte is a typical, medium-sized medieval fantasy village. It's a wonderful place to live, work, and explore, either as a citizen, or as an adventurer passing through town.
One day, the entire city is thrown into chaos as a cataclysmic explosion destroys much of Town Square. A purplish-black crystal of bizarre design erupts from the aftermath, and hordes of chaotic, evil, and undead monsters wade out of the obsidian depths beneath it. A third of the townsfolk are slain in the eruption and the first few minutes of monsters emerging.
What the PCs do, both before and after the explosion that tears the earth and the city's way of life asunder, will set in motion events beyond their understanding or comprehension.
Dark Obelisk: Berinncorte is a massive, urban sandbox adventure that begins an ambitious and epic Adventure Path.
Although a fully-detailed and realized campaign setting is planned, you may easily "place" Berinncorte (and this adventure!) anywhere in your existing campaign.