Wiktionary
literary device
n. (context literature English) An identifiable rule of thumb, convention, or structure that is employed in literature and storytelling.
Usage examples of "literary device".
This was the reason Americans shot each other so often: It was a convenient literary device for ending short stories and books.
Of course you don't need a time machine to do that - the flashback is a standard literary device.
Using this same effective literary device--seeing and understanding the world through the eyes and mind of the leading character--Solzhenitsyn presents an unadorned and starkly disturbing picture of life in a Russian concentration camp.