Christopher Vogler describes seven archetypes who appear in stories.
The hero or heroine is the classic protagonist of the story with whom we associate most. They embody our most aspirational values and put higher duty and the welfare of others before their own, even to extreme forms of self-sacrifice. Achieving the goal of the story may thus be achieved only at terrible personal cost, although the hero may gain much personal learning and growth in the transition.
Heroes can be willing or unwilling, deliberate or accidental, solitary or leaders, already-recognized as a hero or start out as an ordinary person.
The mentor helps the hero in some way, furnishing them with important skills and advice. They may appear at important moments to help the hero get over an obstacle, then disappear (perhaps to mentor another unknown hero).
Typical mentors are old and wise. Although they may also be younger, they are still likely to be older than the hero as they offer their superior knowledge and experience in support. Perhaps once they were a young hero themselves.
The act of giving reminds us of the generosity to which we must aspire. The receiving of the gift may well be seen as reward for courage and self-sacrifice.
The Threshold Guardian provides the obstacles to the hero at transitional points in the story. To get past the guardian the hero must fight them, answer riddles, solve problems, give a gift, and so on.
The Threshold Guardian is often neutral, neither supporting nor opposing the hero, although they also may be allied to the antagonist or even a potential ally.
Thresholds appear before the hero sets out on their journey, before they enter the final 'lion's den' and at critical scene changes. Crossing thresholds symbolize change and points of growth in the hero's character.
The Herald announces important events verbally, telling us what we do not realize or emphasizing the importance of an event. In particular, the herald provides the information that triggers the hero into original action.
The herald need not be a professional announcer nor even a person - a message on a scrap of paper or a radio broadcast can serve equally to trigger change.
The Shapeshifter represents uncertainty and change, reminding us that not all is as it seems. They may be a character who keeps changing sides or whose allegiance is uncertain. They act to keep the hero (and us) on his or her toes and may thus catalyze critical action.
A typical Shapeshifter is a person of the opposite sex who provides the love interest and whose affections vary across the story. Other characters may also be shapeshifters, including Mentors, Guardians and Tricksters.
The Shadow is the opposite of light and provides the tension of anxiety and fear in the story. The Shadow is often opposes the hero and is typically the main antagonist. They may also be people who provide obstacles along the way, although not as a guardian.
The hero must struggle with the Shadow, somehow overcoming the opposition they provide.
The shadow also represents the darker side of our own nature, as in Jung's Archetypes, and it is disquieting to recognize them as somehow related to ourselves.
The Trickster provides entertainment in the story through wit, foolishness or other means. They may be wise, as in the Shakespearian fool, or may be criminal in their deception. They provide further uncertainty and keep us (and the hero) on our toes.
The Trickster may remind us to lighten up and see the funny side of things. They also remind us not to be naive and to expect the unexpected.
Vogler, Christopher (1992). The Writer's Journey: Mythic Structure for Storytellers and Screenwriters. Studio City, CA.: Michael Wiese Productions