The term "initiation" as a universal theme often refers to a coming-of-age experience or the moment when a character undergoes a significant change or growth. In literature, an example of this theme could be characterized by a young protagonist facing challenges that lead to personal growth or a deeper understanding of the world.
For example, in the novel "The Catcher in the Rye" by J.D. Salinger, the protagonist Holden Caulfield experiences various initiatory moments throughout the story that shape his understanding of adulthood and identity.
In terms of a "mountain" or "forest" metaphor, consider "Into the Wild" by Jon Krakauer, where Christopher McCandless's journey into the Alaskan wilderness serves as a physical and metaphorical initiation into adulthood, confronting his ideals and his understanding of life.
If you meant a specific item or element in a different context related to these themes, please clarify for a more precise answer!