Spoiler

Spoiler 

Refers to stories or comments which contain scenes or information crucial to a specific episode of the canon material, often about major plot points or character developments. The accidental or deliberate revelation of the information prior to seeing the canon material usually "spoils" the surprise/pleasure for the reader in discovering the information themselves. Warning for spoilers allows readers to make the choice themselves about whether or not they wish to proceed and discover the unknown information willingly or skip the story until later, instead of having the surprise unpleasantly ruined when they least expected it.