I have six flat-characters and two-rounded, the protaganist and his love interest. Eight characters is pushing the boundaries, when five or six is considered to be the norm. But they are all vital to the plot and storyline.
A brief explanation of what I mean to novice writers: A flat character is a minor character in a work of fiction who does not undergo substantial change or growth in the course of a story. Also referred to as "two-dimensional characters" or "static characters," flat characters play a supporting role to the main character..
A round character is a major character in a work of fiction who encounters conflict and is changed by it. Round characters are more fully developed and better described than flat, or static, characters.
I'm never sure where you draw the line with this description, Adrian. If I take the example of my Nanowrimo novel rather than the series I definitely have two main characters, then four more I hesitate to call flat and then a small cast of people I would class as a bit more than extras. Say ten of those? They are the ones I would call flat characters as they mostly have a specific plot purpose and are quite 2D. Whereas my four supporting characters do go through some development themselves (although admittedly not as much as the two main characters.)
And now I think of it the pattern is the same in the series. Three main characters, probably as many as ten supporting them and then dozens of extras. I really think the extras better fit the description of flat character.
Hi Adrian, (same name as my main male character)
I have around five to six, plus the two main characters.