Not that I ever meant to write a sequel or a series. Originally, Death Sword was a stand-alone. I'd finished the book and had started writing another one, when Samael, the antagonist from Death Sword began grumbling he wanted to tell his story. Our conversation went something like this:
Samael: "I want to tell my side of the story."
Me: "I'm done with Death Sword. I've moved on to another book."
Samael: "But you made me look like the bad guy."
Me: "Um, because you were? Now move along. I have too many characters running around in my head, and you need to leave."
Samael was stubborn, and he continued to nag at me, so I decided fine, I would do a little more research about him, and maybe that would make him happy. Not that I hadn't researched him before, but I had some new material I'd acquired recently, and not only did I find something about him I hadn't seen before, it was something that convinced me that yes, I had to continue the story.
Now, I won't go into details about how Serpent Fire became my bete noire. I rewrote it twice, and finally ended up merging it with Devil Inside, a book that, in my humble opinion, was a bit more "together." Either way, not all is lost. I'm using material from SF in another book.
This new version of SF/DI will go through another round of revisions, but I hope to submit it this year, along with the novella, Hell on Earth, a spin-off of Exterminating Angel.