The dead city of Mishtan was once a great power centre to the undead, but as a dwarven kingdom of old settled upon it, fighting off the ghouls and ghosts, and slowly mining down into Mishtan, it soon became apparant that neither party was going anywhere.
A pact was formed after years of skirmishes and today the dwarves and their priests live in 'harmony' with the dark city of Mishtan and it's underdark city of Nocturne.
The Copper are so named for primarily living on the surface and thus having their skin bronzed by the ever burning sun over head.