Deus ex Machina
An unexpected, artificial-seeming intervention that abruptly resolves a story’s conflict.
A deus ex machina is a sudden device—a rescue, coincidence, or new power—that untangles a plot the characters could not resolve on their own. Writers sometimes use it deliberately for effect, but it is often criticized as an easy escape from a corner. The term comes from ancient theater, where a god was lowered by machine to fix the ending.
Example
Earth’s unbeatable invaders are felled not by human effort but by ordinary microbes, an outside force that ends the crisis for the helpless characters.
The War of the Worlds · H. G. Wells
See it in action
Analyses on StoryBites that use deus ex machina: