From a H.N. POV there are two types of characters: historical and non-historical, or fictional ones. Both of them, though, must be realistic and believable characters, this is, not overtly fantastic (like, say, a Dragon, or a honest lawyer... ahem! :-)
Historical characters are the ones primary sources give us well documented, and they come in two flavors, real and mythical. The real historical characters are those that we can have a high enough certainty that they were real some time in the past (like king Alphonse X of Castilia, for example). The mythical ones are well documented in primary sources but, well, don't seem to be real (at least, so far in Historiography, like el Cid presented in the epical poem, or --let's be a bit polemic-- Jesus Christ as presented by the Christian sources).
Fictional characters, OTOH, come in many flavors, but there are also a couple of them that shine over the rest, at least for me, at the moment. Those are the companion and the gossiper. The companion is a character that goes with the (presumably historical) primary character (starring, or a similar role, kind of Beta male to the Alpha male, or the Princess for the Hero, etc...) and the gossiper is the one that's everywhere and can tell everything to everyone. There are many more (the antagonists made to make the main character shine by contrast, or the redshirts, created just to fill-in and, eventually, die, a concept I learned from Star Trek; etc...) but these will suffice for the moment.
Here you have the classification so far, in a glorious display of HTML mastery (ahem!):
- Historical characters
- Real characters
- Mythical characters
- Fictional characters
- Companion character
- Gossiper character
Let's follow this classification with my novels (the ones you can watch on the counter in the left side of the main blog page):
- The Goth:
- Real characters: Alaric, Ataulf, Valens, Stilicho, etc...
- Mythical characters: none
- Companion characters: Cornelius Theodoricus
- Gossiper characters: Domitius Ahenobarbus
- The Libyan:
- Real characters: Inaros, Megabyzos, Amyrteos, ...
- Mythical characters: Kharitimides, Megabazos
- Companion characters: Leucon
- Gossiper characters: Argyros, Megabazos, Amyrteos
- Damned Linneage:
- Real characters: none
- Mythical characters: Laius, OEdipus, Yocasta, etc...
- Companion characters: Aspisides
- Gossiper characters: Elektra Dorothea
I have, deliberatedly, left many important character behind, else I would need a huge post and lots of time.
You can see, by comparing, the very different feeling each novel presents: The Goth is strongly based around real characters (re-created by me, but real, who did real things), with some fictional characters to help me to present different POVs, or aspects from a different perspective.
The Libyan, on the other hand, is based on little historical evidence, and I am forced to supply most of the details, and therefore the fictional characters are very important.
Damned Lineage is a historical synthesis of different, related Greek myths on the Bronze Age, deconstructed so to re-create historical settings that could have plausibly derived in the creation of the myths. Therefore all (or most, anyway) characters are mythical or fictional.
The challenge in each novel is different, and characters need to support me and help me make them. I try to be as realistic as possible, and as believable as possible, using the techniques I can (playing, basically, with the characters) in order to provide the best novelling experience I am able.
Maybe another day I'll complete my own theory. Those who have formal studies about writing, etc, are more than welcome to crash my feeble attempts to formalize a bit my work, I am "playing by ear" in this... But please, be gentle... :-)