Well, the seed of the idea was from this music video. We'll wait while you watch it.
I'd had the two guys from the video knocking about it my head for years. I knew I wanted to write about them, but I didn't really want them to be ghosts, like here. I'd been studying social media and reading various blogs on self-publishing, and I decided "Hey, I can do that." I just needed the characters and the story.
One day, driving to meet a client, I remembered the video and the two guys, and I decided to use them in a book. The one in white was easy. He was my vampire. (By the way, the artist's name is Paul van Dyk, and yes that is the origin of Paul's name.)
Then I decided the one in black would be a warlock. Not a wizard, but a warlock. Everyone writes about wizards. Not so many people about warlocks. Originally, Dafydd was supposed to have a day job as a stage magician, but I never quite got into the idea, so he became a multi-level marketer instead. Because that is so much cooler. ;) Oh, the singer in the video is Wayne Jackson. I didn't want my main character to be named "Wayne," so I named him after my son instead. But one of Dafydd's favorite singers is Wayne Jackson, so I do keep the connection, after a fashion.
Once I had the basic character ideas and worked up a bit of their background, writing them was easy. Well, relatively so.
There's where I got the idea for the characters. Tune in next week when I answer the other common question. Why did you make Dafydd gay?