From IFWiki

This is a category for articles containing spoilers for works of interactive fiction. Examples of possible spoilers include: a list of characters in the work, a summary of the plot or backstory, a list of amusing things to try, a list of possible endings, a walkthrough, a map, a glossary of invented terms used in the work, a list of conversation topics understood by the NPCs, and so on.

CAUTION: If you don't want to have a work spoiled for you, then don't read that work's spoiler page!