Taboo
A prohibition against a specific action, often serving as a plot device in fairy tales when characters violate forbidden rules.
Taboos feature prominently in fairy tales as narrative devices that create conflict. A character is told not to do something (open a door, speak a name, look behind them), and their inevitable violation of the taboo triggers the story's central crisis. In Propp's morphology, this corresponds to the Interdiction and Violation functions. Examples include Bluebeard's forbidden room, Psyche's prohibition against looking at Cupid, and Lot's wife being told not to look back at Sodom. Taboos in folklore often reflect real cultural prohibitions and serve as cautionary elements about the consequences of curiosity or disobedience.