Drew Tuzson said:
Here's the whole thing, bullet pointed, in review. It more or less paraphrases the rule book:
- These rules for playing dupes only apply to unique cards (ones with a black flag symbol before the title).
- You must have a unique card in play that you own and control.
- You must have a copy of the same unique card -- as determined by title -- in your hand.
- When it is your turn in Marshaling, you may attach the copy in your hand to the copy already in play. This is considered "playing a dupe" and doesn't cost you any gold.
- If that card would be killed, discarded, returned to hand, returned to deck, returned to Shadows or otherwise removed from play, you may discard the dupe to save the original copy.
- The duplicate does, and pretty much means, nothing else beyond this "save" function.
- Since the original copy is "saved," whatever effect tried to remove it from play is considered to never have been successful. The original copy thus never leaves play to being with.
I'm not sure I can explain dupes any more clearly than that.