Probably the question I’ve received most often about A Soul to Steal is whether its central mythology, a legend called “The Prince of Sanheim,” is based on something real. I’ve had friends admit that they Googled the term after finishing the book, and others who suggested they had heard of it before.

There is very little as gratifying for a writer, since the truth is that I made up the entire story. What makes me happy is that it doesn’t feel fake. A good mythology should seem real or vaguely familiar, the kind of thing you heard once but have since forgotten.

I’m not sure exactly when the idea came to me. I know a lot about Halloween, and much of what we think we know is not actually true. Occult fanatics and religious zealots in the 19^thcentury invented a past for All Hallow’s Eve which has very little to do with actual history.

Instead of rejecting that, however, I wanted to embrace it. I wanted a legend that drew from those old myths—real and fictional—and created something new. And I needed something that would go to my central theme: the nature of fear.

What I wanted to know was this: do your fears define you as a person? What would it be like if your worst fear—whatever that is—suddenly took shape? Would you have the strength and courage to face it?

I also wanted something that drew from a dark place. Fear is a powerful thing. We tend to view it negatively, but it’s also a great motivator, among other advantages. Still, it cuts both ways. It can either save you or paralyze you, depending on the person and circumstances.

So I needed a legend that drew on old Halloween myths, explored the nature of fear, but also was something unique.

Here’s what I came up with. Do you want to hear a new Halloween legend? Pull up your chair and I’ll tell you a story: Centuries ago, a Celtic tribe was on the verge of annihilation, facing the increasing incursions of a rival. In desperation, they made a deal with Sanheim, the Celtic god of the dead. Despite the fact that most of their young people were killed as a result of the neighboring tribe’s attacks, they agreed to sacrifice one man and one woman to Sanheim. They tied them to a post, bound their wrists together and left them there to die.

But they didn’t die. A few days later, they returned to the village and the young man—who had seemed like just a boy before—was now a powerful warrior. The woman was his priestess. The town elders were frightened, but pleased. The two left the next day to wreak vengeance on the rival tribe. Except when they returned, instead of taking orders from the town elders, they took control.

The two had immense powers—and were intimately bound together. When there was a battle to be fought, the man led the charge. But it was the woman guiding the tribe, making most of the decisions. Apart they were nothing. Together they were what became known as the “Prince of Sanheim.”

But there was a weakness. Their powers waxed and waned with the changing of the seasons. They were strongest at Samhain, the harvest festival we now call Halloween. They were weakest the next day, what Christians call All Soul’s Day. And the power they wielded tended to corrupt them.

Every generation, a man and a woman had the chance to become the Prince of Sanheim, but there was a catch. The man must first face his Cennad—a Celtic word for ambassador—that embodied his worst nightmare. If the man could defeat his Cennad, he and the woman would have access to great powers. The woman, too, would have to face her own test, but of a different nature.

That was the basic legend, but I couldn’t really stop there. I didn’t want to just have an old myth with no echoes through history. So I invented stories for several Princes of Sanheim through the ages. In the original version of the novel, there were flashbacks to many of them so that the reader got a greater sense of their powers and vulnerabilities.

In the end, however, I cut most of that, simply because my novel already has a lot going on. The entire backdrop of the Prince of Sanheim unfolds while on the hunt for a serial killer with his own twisted history and I was wary of throwing too much at the reader.

The story I did tell was that of the most famous Prince of Sanheim: a Romantic-era poet named Robert Crowley. On Halloween night in 1873, he hosted a party at his estate in Scotland. Over 50 men showed up and history does not record the number of women who also attended. What is important, however, is that all but one disappeared. Only a man named Horace Camden survived and he shouted to anyone who would listen that Crowley had found his bride and become the Prince of Sanheim.

The event was so mysterious it gave birth to a creepy rhyme: “Fifty men went up a hill, none of them came down. Fifty men went to see him, but none of them were found.” Camden went on to become a priest of the movement, talking about the coming of the next Prince of Sanheim.

The final step was to set up an environment where this new legend was born again. Quinn O’Brion and Kate Tassel, the main characters of the novel, don’t know anything about the “Prince of Sanheim” when the book starts. Instead, they are more worried about catching the killer named Lord Halloween before he strikes again. But as the novel goes on, they eventually realize that the key to finding the killer may lie in uncovering the mystery of the ancient Celtic myth.

They also have to learn something else: you are what you fear.

The novel can be bought for Kindle here. 

This post was originally published in October 2011. This year’s guest post can be found here: http://bit.ly/NBRGuest.