Plot device

A plot device is a small machine with a relatively simple design. It is designed to initiate changes in a story's plot to aid and assist the character that activated it.

Design
A plot device looks like a small cube, about the size of a standard brick, cut in half, made of a shiny silvery metal. On one side is a large red button.

Plot twists are similar in design, though appear to be made of solid gold.

Effect
Upon activation of a plot device, it will disappear in a puff of smoke. Almost immediately, something will happen that is decidedly out of the ordinary, but assuredly to the activator's benefit. However, after this, something else will occur; a negative side effect, to balance out the positive effect. The negative effect is usually temporary, and tends to affect the narrator more than anyone else. If another plot device is activated to negate the negative side effect of another plot device, then that plot device's positive effect will be cancelled out as the negative side effect of the new plot device.

Plot devices cannot be used to undo an event that has been brought about by a plot twist.

Name origin
A "plot device" is a term used to describe something inserted into a story for the sole purpose of advancing the plot or to help characters overcome some sort of difficulty.