Changing a character's archetype
Question: Is a character's archetype based on its final state when the story ends, or can a character's archetype change one or more times during the course of a story?
Dramatica considers a story to be a model of a mind attempting to resolve a problem or move from disharmony to harmony. Within that framework, characters represent different conflicting drives which impact how the story goal will be resolved.
At the end of the story, the problem will have resolved itself one way or the other, which means the characters no longer have the potential to affect the outcome. Therefore, they tend to be less driven at that point.
So to answer the first part of your question, it is the drives a character possesses in the course of the story that identifies their archetypal role, not how things stand with them at the end.
The second issue, whether a character's archetype can change several times, it a little more complicated...
First, a character may have a different archetypal role within different plotlines. For example, in Star Wars
, R2D2 is a Sidekick to Luke in the overall story. However, when he is on his own (or with C3P0) in act 1, he functions as the Protagonist--pursuing the goal of taking the plans to Obi wan Kenobi. Similarly, C3P0, who also functions as a Sidekick when
interacting with humans, takes on the role of Skeptic when he is alone with R2D2.
Whenever you switch to a different character's point of view, the roles can shift in this way.
It is also possible for characters to hand-off their roles. For instance, let's say you have a Guardian character--a martial arts master who is training the Protagonist for a task. The Guardian may have a nephew who functions as his Sidekick. Let's also say that at some point in the story, the Guardian is killed, but at some point after that, you need a character to act as a conscience or provide help to the Protagonist. One option is to let the nephew take over the Guardian function. He might have a line like "I know what my uncle would have said. He would have told you to X." Or perhaps he ascends to his uncle's throne (figuratively) and reveals himself to be a source of wisdom in his own right.
That said, it is important that your characters appear consistent. Any changes they undergo must make sense, otherwise they can seem less believable to the reader. Basic personalities can develop, but they are seldom erased. An Emotion character is unlikely to suddenly become a Reason character and vice versa, though circumstances may force him to venture outside his comfort zone or temporarily suppress a part of his personality.