Ptolus is an urban campaign setting. However, it is also one that deals with dungeon delving and subterranean exploration. In your own Ptolus Campaign, you can probably expect about a fiftyfifty split between dungeon adventures and urban adventures. The latter involve a surprising array of organizations and of individuals that live in this less-than-typical fantasy city.

As a setting, Ptolus should prove a somewhat realistic interpretation of a place in which dungeon explorers really do plumb the depths of a gigantic underground labyrinth filled with treasure, monsters, and traps. As much as possible, many standard tropes of fantasy adventures, including “dungeons,” are presented in a fashion that makes logical sense.

While late medieval culture provides one building block of the setting, it’s not the focus that you might think it to be. The Core Rules are that focus. So, while Ptolus is based strongly in historical reality, many notions from real-world history that often hold true in other campaigns (most adults don’t believe in monsters, everyone’s bewildered by magic, you never see lizard men walking down the street) are not present here. Instead, Ptolus is a campaign where the Core Rules and all that they imply hold sway. That means “monsters” are common. Wizards are everywhere. Lots of people walk around in plate armor. Humans strolling down the street rub shoulders with elves, dwarves, halflings, gnomes, half-orcs, and even stranger beings.

In a way, this campaign is “the d20 System rules with the volume turned all the way up.” Creating this city did not involve building a fantasy world first, then adapting the rules to make it work. Just the opposite, really. As a setting, Ptolus has been under the influence of the Core Rules for a long, long time. The things that make d20 fantasy unique—the prevalence of magic (including the specific spells we all know), the ever-increasing power of individuals, and the creatures of the MM—have shaped the reality of Ptolus. And because the designer of Ptolus used this setting as a playtest backdrop as he worked on the design of the Third Edition Core Rules, Ptolus influenced the d20 System rules as well. This is a setting steeped in game history and significance.

That doesn’t mean Ptolus contains nothing new, however. As the city developed, new material grew out of the process. The firearms, creatures, spells, races, and foreboding atmosphere all came very naturally.

The Ptolus Campaign is a fantasy that some would label “dark,” although it’s as much about rising up out of the darkness as living within it. It is clearly an urban fantasy, for the campaign takes place entirely within or beneath the city of Ptolus—a place with a vast history of dark secrets waiting to be discovered.