What is a long narrative poem about a hero's journey called?

A long narrative poem that details a hero's journey is known as an epic. Epics are characterized by their grand scale and significant themes, often involving heroic deeds, adventures, and events that are foundational to a culture. They typically start with an invocation to a muse and often include supernatural elements or larger-than-life characters. Classic examples of epics include "The Iliad" and "The Odyssey," which recount the adventures of heroic figures.

In contrast, a ballad is usually a shorter narrative poem that tells a story, often of love or tragedy, but lacks the same level of grandeur and complexity as an epic. An ode is a lyrical poem that expresses emotion and is often addressed to a particular subject, while a sonnet is a specific form of poetry consisting of 14 lines that typically explores themes of love or nature. Thus, the distinct characteristics of an epic make it the correct answer in this context.