|Type(s)||Treasure - Prize|
When you play this, + per unused Action you have (Action, not Action card).
(This is not in the Supply.)
Diadem is a Treasure-Prize card from Cornucopia. It is not in the Supply, and can only be gained through playing the Tournament card. It gives you for each unused Action you have—amazing when you have an engine with too many villages, but not useful in Big Money games.
 Official FAQ
- When you play Diadem, you get an extra +Farming Village (which gives you +2 Actions), then Diadem, Diadem will give you an extra + , for total. per unused Action you have. This means Actions, not Action cards. So for example if you play
- If you play no Action cards at all on your turn, you will have one unused Action, so you will get total from Diadem.
 Other Rules clarifications
- It is possible to steal Diadem from another player by using Thief.
- If you play Diadem during your Action phase, such as with Black Market, it does not use up your remaining Actions; it only gives equal to their number.
 Strategy Article
There isn't a strategy article for Diadem.
It's a great card to pick up if you, for whatever reason, have an oversupply of Actions. Maybe you built a City stack for the +Card, + , and +Buy, and don't have enough terminals. Maybe your Throne Room/King's Court/Grand Market engine is generating a huge surplus of Actions.
However, in a Tournament game, this will rarely be the case, since Tournament games are often a race to the first Province, with no time to set up a huge engine. Even so, Diadem will often be worth, and can be a good Prize to take if the situation demands it.
 English versions
|. When you play this, + per unused Action you have (Action, not Action card). (This is not in the Supply.)||Cornucopia 1st Edition||June 2011|
|. When you play this, + per unused Action you have (Action, not Action card). (This is not in the Supply.)||Digital version has a cost ofrather than .||Cornucopia 2nd Edition||March 2018|
 Other language versions
 Secret History. Return this to your hand." It was a cute combo with Villages, but useless without them. I then tried some "choose one" versions, which solved the problem of it sometimes being dead, but didn't make the actions-to-money part any better. I eventually gave up on it, and well here it is at last.