Perhaps the main theme is growth. The father's growth as an individual while also seeing his children grow up, and how they influence each other's development.
It could be about family bonds. The father's role in creating and maintaining a strong family unit.
The main theme could also be discovery. John might be exploring a new world or situation in the story, and the 13 elements could represent 13 different discoveries he makes. This could include self - discovery, discovery of new places, or discovery of new ideas.
It's hard to say without reading it, but perhaps it could be about fear and the unknown. Ghost stories often revolve around these themes.
Another possible theme could be transformation. Maybe the person in the story had a negative view of their skin at first, but through various experiences, they had a transformation in their attitude towards it, and it became a symbol of their personal growth and strength.
The main theme could be friendship. Since it's about four friends, it's likely to revolve around the relationship between them.
One possible main theme could be transformation. If the boy is somehow related to a stone, perhaps he goes through a transformation similar to how a stone can be shaped over time.
It could be about pain and punishment. The whipping being the physical pain and the whole situation representing the punishment for some sort of misdeed.
One possible main theme could be secrecy itself. The whole story might revolve around how Terrius keeps certain things hidden and the consequences of that secrecy.
Perhaps the main theme is love. A father's love for his children is often a powerful and central theme in such stories.
Well, it could be about self - discovery too. Maybe the main character returns to the father's house and through the experiences there, discovers things about themselves, like their roots, their past, and how it shapes who they are. It's often the case in such novels that the setting of the house serves as a catalyst for self - exploration.
The main theme is survival and the horror of war. It shows how a young girl endures the Khmer Rouge regime in Cambodia.