Dungeoneer: aka "Dungeon Keeper"
Long ago there was a wonderfull pc game called "Dungeon Keeper" where you managed an army of monsters while exploreing the underworld for resources. All the while an army of invaders keep approaching to work against you. This sounds incredibly similar to the gameplay description of Dungeoneer. The down side of this perspective is that each player as a hero plays against one another instead of against a single dungeon keeper. Then you have what might seem like an underdeveloped trade/resource system for the dungeon lord.
I honestly believe that with a few tweaks to the graphics and gameplay that this game could be repackaged as "Dungeon keeper" the card game and due to saturated market recognition, SELL. Add in better rules for combineing expansion and Voomp. More sell. Personaly I like the idea of either square or hexagon tiles. But thats just me.