Part of Call of Cthulhu's appeal is its ability to interpret the Lovecraftian Mythos on a variety of levels. With a d20 system, these levels are more specifically grouped such that power dictates a particular kind of play style. For example:

• 1st through 5th level: Gritty. Cultists can kill characters. A crime scene is a challenge. Resources are hard to find. The characters often survive by the skin of their teeth, or don't survive at all. In literature, this encompasses the majority of Lovecraft's original works.
• 6th through 10th level: Procedural. The characters are now experienced professionals. They've survived their fair share of serial killers, aliens, and ghosts, and probably have a process or plan to deal with them. When they face the supernatural a second time, they know its weakness. When they deal with the undead, they know when to fight and when to run. There are a few experienced Mythos hunters in Lovecraft's tales, but not many. Traditional Call of Cthulhu campaigns seem to hover around this level.
• 11th through 15th level: Pulp. The characters now have access to items and powers that exceed mortal men. They may look normal, but they're action heroes through and through. They can take on minor Mythos servants on their own. Yes, that includes Hounds of Tindalos. For an example of a Hound of Tindalos getting shot up, see John Bell in Jeffrey Thomas' Bones of the Old Ones short story.
• 16th through 20th level: Superhero. If things started getting out of control after 11th level, by 16th they're now clearly more knowledgeable and capable than mere mortals. These are the sorcerers supreme, the ninjas, the gunslingers, the badasses who take out multiple opponents by themselves. They can start to challenge Great Old Ones and probably foil their plans, if they're smart and lucky. The Titus Crow series provides a template for how a campaign at this power level might run, where psychics are commonplace and Mythos beings fear them.

The problem with this inevitable power creep is the scenarios themselves. I've structured the campaign such that the opponents become increasingly more powerful; a ghoul is a much more appropriate threat to a Gritty or Procedural level game, while Chthonians are great Pulp or Superhero-level villains.

Eventually, the campaign is going to have to end. As George put it, "but it should end just as we reach 20th level." That's a difficult balancing act between players (just which player is supposed to reach 20th at the end of the game?) and the pace of the game (not all scenarios give the same amount of experience).

Your Turn: I've got my campaign's conclusion planned. Do you?

Michael "Talien" Tresca is the National RPG Examiner