Treasure of the Black Dragon
A hundred years ago a group of adventures found the lair of a evil black dragon. The dragon had been terrorizing the local people and rumors had spread that the dragon was planning to bring destruction to the entire continent. The adventures decided that they must do something to stop this, and so valiantly charged to the dragons lair. The fought the dragon but ultimately could not defeat him.
The instead stole the source of the dragons power and fled, hoping to hide it away. While the dragon was severally weakened it was not powerless. Each of the adventurers were hunted down and killed.