What you own when you own a story is the intellectual property in the story. It’s an idea. We lawyers like to call it intangible property – that is, you can’t pick it up or touch it. What you actually own has no physical existence of its own.
- Original storyline using characters from a book or game – you own the plotline, but you don’t own the characters. To sell this, you would need to change the characters;
- Storyline derived from the game using characters from the book or game – bad idea. Go write something of your own!
- Storyline derived from the book or game using original characters – you won’t be able to sell that story without infringing the book or game owner’s intellectual property, but you can take the characters and re-use them in an original plotline. Note that if you use the names of characters from that other work, but your characters are not actually true to the characters in that other work, the character is yours but the name is not. You could change the names and re-use the characters. However, if the character is properly the property of the owner of the other work, merely changing the names won’t save you;
- Original plotline using original characters – the only way this would be tied to the book or game would be if you had used names from the book or game, either characters or places. If we assume you have used those names, but the characters are not true to the descriptions in the game, you can change the name and away you go.