The story of the city that the adventures start in is a tragic one. In the middle of what has become the Mega-Dungeon, there was a Dwarven Hold. This hold had 4 main parts:
1) "The Place With Many Names:" This was the heartland of the Dwarven Hold until about 350 years ago. The Hold had been assaulted on all sides by numerous enemies, who wanted the Hold's riches for themselves. No faction controls the Hold now, it is broken into many small territories controlled by different powerful creatures or groups. This area is the closest to the city that is still held by the Dwarves. No group has been able to claim the Hold for themselves since the Dwarves retreated.
2) "Breeding Pits:" This was once the breadbasket of the Dwarven state. It is now a fungus and mold kingdom. Many forms of semi-sentient fungi and molds live here, and have even created some symbiotic relationships. These relationships could mean that what appears to be helping one faction of the area, is actually hurting it.
3) "Adventurer's Guild Hall:" This is the starting city of the campaign, the one piece of the Hold still controlled by the Dwarves. They have let anyone willing to help them fight to regain their former glory inside their walls. Not all are good, but each has a purpose in the war effort to reclaim the Hold.
4) "Peace Pits:" Once this level was a thriving multicultural bazaar. The Dwarves allowed any race to trade their wares here, duty free. It has since been overrun by individuals and small factions, each fighting for a territory and the secrets that may be held within.
These areas are intended to be the early levels adventuring areas for the campaign. They are still rough sketches in my mind right now, but I hope to make the Hold and its sub-levels a breathing character of the campaign, just like any merchant or villain.