A classic 3.5e Campaign set in a heavily modified version of Greyhawk.
It will start in the city of Verbobonc.
The north Is encompassed by an ancient massive arcane explosion called the arcane cataclysm(there are many names given this fallout area). It is thought to be a result of ancient warring great magic civilizations that ended up using an arcane weapon rivaling the most powerful hydrogen bombs of today. The ancient ruins of these grand magic civilization dot the land, their time fell into a dark ages and massive worldwide devolution of technology/civilization/and magic. Only until the last 1000 years civilization are becoming large enough to rediscover the past connections to the great arcane.