The process of writing a sequel begins with conception. I know the time period I want to write about. I know the historical events I want to relate in the novel, but in the beginning I don't always know who my main character will be.
For example, when I began conceptualizing the sequel to "The Wind in the Embers", the book that would eventually become book two of the Amulet Series, I didn't know who would stand at the center of the story. I could have used a character from the "The Wind in the Embers", but I didn't have to. The main character for the second book could have been an entirely new character who hadn't appeared in the first book at all, as long he or she interacted with some of the characters from the first book, for the sake of continuity.
On the other hand, there were plenty of characters from the first book whose stories could have been carried forward in the sequel. Placidius (who is the Emperor Valentinian III), Flavius Aetius, and Justa were just a few of the characters whose stories were only partly told in “The Wind in the Embers”. So any one of them could have become the main character in the sequel.
But I also had to consider the audience I was reaching with “The Wind in the Embers”, a book about a remarkable woman, whose primary appeal would be to female readers. If I wrote the sequel about Flavius Aetius, some of those readers might be disappointed. So I needed a woman.
I couldn’t use Galla Placidia, because the juiciest part of her story had already been told in “The Wind in the Embers”, and I couldn’t use Justa because the historical material about her was so scant, and, besides, Justa was an ideal antagonist (she is such a conniving bitch). So I needed someone else.
I start researching female historical figures whose lives touched on my story, and I didn’t have to go far.
Licinia Eudocia, the daughter of
the Eastern Roman Emperor, who weds Placidius at the end of “The Wind in
the Embers”, was perfect. First, there was enough historical material to
get an idea of who she was in real life, but more than that, her story was as good as Galla’s! There was infidelity, murder, rape,
kidnapping, and more. (The Romans left no boxes unchecked when it came to real life drama.) So my mind was made up. Licinia Eudocia would become the main character of the second book in the series, which was eventually entitled, "The Shadows of Nemesis".
From there I began to shape the narrative around what was known about her life and the historical events that impacted it. Thus, I began the groundwork for the sequel.
Malcolm