A plot device or plot mechanism is any technique in a narrative used to move the plot forward. A clichéd plot device may annoy the reader and a contrived or arbitrary device may confuse the reader, causing a loss of the suspension of disbelief. However, a well-crafted plot device, or one that emerges naturally from the setting or characters of the story, may be entirely accepted, or may even be unnoticed by the audience.
Many stories, especially in the fantasy genre, feature an object or objects with some great magical power, such as a crown, sword, or jewel. Often what drives the plot is the hero's need to find the object and use it for good, before the villain can use it for evil, or if the object has been broken by the villains, to retrieve each piece that must be gathered from each antagonist to restore it, or, if the object itself is evil, to destroy it. In some cases destroying the object will lead to the destruction of the villain.
In the Indiana Jones film series, Jones is always on the hunt for some mystical artifact. In Raiders of the Lost Ark, he is trying to retrieve the Ark of the Covenant; in Indiana Jones and the Last Crusade, Jones is on a search for the Holy Grail. This plot device is also used in the Arabian Nights tale of "The City of Brass," in which a group of travelers on an archaeological expedition journey across the Sahara to find a brass vessel that Solomon once used to trap a jinn.
Several books in the Harry Potter series orient around a search for a special object. In Harry Potter and the Philosopher's Stone, Harry believes there is a magical stone in Hogwarts with special powers. Lord Voldemort needs this stone to bring back his body, and Harry looks for the stone first to prevent Voldemort's return.
The One Ring from J. R. R. Tolkien's novel, The Lord of the Rings has been labeled a plot device, since the quest to destroy it drives the entire plot of the novel. However, as British Classical scholar Nick Lowe puts it: "Tolkien, on the whole, gets away with the trick by minimizing the arbitrariness of the ring's plot-power and putting more stress than his imitators on the way the ring's power molds the character of its wielder and vice-versa."