Well, the concept we were working from was this;
5,000 years prior to the campaign start, there were two major alliances warring with each other. Essentially, magic became the arms race between them - up until this point, even divine magic users had never had access to major magics, because the gods of this world were pretty hands off. Anyway, the two sides were both performing experiments, and researching new and more powerful spells until things really began to get out of hand. Teleporting assassins, new armies of constructs and undead, eventually even things like the city bomb started to come into play. Long story short, the gods tried to intervene through their followers, but the world managed to blow itself up - and somehow severed the control the gods had on the world. (They're connection was still there, they just had no control over it, so clerics, druids etc still received their spells Only a handful of pockets of civilization managed to survive. One of these was headed by the lead researcher of one side - he saw the damage caused and vowed that it would not happen again. Blaming the bureaucrats for the catastrophe, he set up a mageocracy, with self contained cities run by magic. In the meantime, many of the experiments managed to break free and survive in the vast wilderness between the cities.
This system lasted for 5,000 years, as long as the leader was alive. But the magic he had found to sustain his life eventually failed, and as he lay ding, the various faction within the government started their small, quiet war. The wizard in the party was apprenticed ti one of the major players, so they ended up getting involved. Not that they knew about that at first^^
The adventures were a fair amount of ruin crawls, with some urban adventures thrown in for variety, and some planar shenanigans later on in the campaign. I think the most memorable moment was probably when the party dropped a city-sized AMF in order to fight one of the enemies, and the gish pulled out an eyepatch and said "fuck yeah, just call me Snake, baby^^" And he gave "Snake Plissken" as his name for the rest of the campaign