Ancient archetype. Also: Friend, Companion. Every hero needs helpers. There must always be someone who shows the way, provides a sounding board for the hero’s concerns, and demonstrates possible alternative courses of action. Distinct from the False Ally, who reveals him or herself as an opponent in the second half of the story. Famous Ally: Ariadne. Modern example: Ron Weasley.
For details, read Relationships Between Characters, Part 1: Allies.
For a list of archetypes, see Archetypes.