A character in a fictional work that is never developed by the author is called a

Explanation:

There are multiple words to describe a character that is never developed by the author. A flat character, for example, is a character that is only defined by one or two traits and nothing else. However, in this case, I think the answer would most likely be a static character, which is a character with little to no development so as not to take away from the story being told.

voracity is the noun corresponding to the adjective voracious, which means (1) eager to consume a great amount of food, or (2) marked by an insatiable appetite. veracity is far more common than the rare voracity, so the latter is sometimes used in place of the former.