You may play an Action card from your hand that you don't have a copy of in play. If you do, +1 Action.
 Official FAQ
- When you play this, you can play an Action card from your hand, provided that you do not have a copy of that card in play.
- It does not matter if you played the Action card this turn, only that it is not in play when you play Conclave; you can use Conclave to play a card that you played but trashed and so do not have in play, like a Pixie you trashed, but cannot use it to play a card you did not play this turn that is still in play, such as a Secret Cave from your previous turn.
- Conclave normally cannot play a Conclave, as that is a card you have in play.
- If you do play a card with Conclave, then Conclave gives you +1 Action, which has no special limitations, and so can for example be used to play another Conclave.
 Other rules clarifications
The discussion topic for Conclave can be found here.
Conclave is a fairly exotic splitter. It is a decent engine card that rewards variety; if you have a sufficient amount of variety in your deck, Conclave can become reasonably reliable. Although it might seem similar to, for example, Conspirator at first glance, it is actually best compared to Festival; assuming it can hit a different card every time, it gives + and +2 Actions, making it a cheaper Festival without the +Buy. Usually you will not want to fight for the split, because Conclave becomes more difficult to manage once you get more of them, and also because it does not draw any cards itself.
If Conclave is the only splitter, engine building becomes somewhat tricky but not impossible. Strong trashing helps a lot, as do cantrips and a variety of draw cards. Conclave is particularly useful in these situations because it decreases the need of buying Treasure cards for payload; in fact, you will likely never need Silver if you are playing a Conclave engine. If there are other splitters on the board, a mix of both Conclave and the other splitter tends to be good, as Conclave likes the variety and the other cards like the money Conclave provides.
- Band of Misfits and Overlord can always be played with Conclave, since they change name upon play.
- Draw-to-X (Library, Watchtower)
- Royal Carriage
- Prince + Conclave + Reserve cards enable you to play and call Reserve cards in the same turn
- Duration cards, since they remain in play.
 English versions
|+. You may play an Action card from your hand that you don't have a copy of in play. If you do, +1 Action.||Nocturne||November 2017|
 Other language versions
Du darfst eine Aktionskarte aus der Hand ausspielen, von der du keine gleiche im Spiel hast.
Wenn du das tust: + 1 Aktion.
|Japanese||秘密会議 (pron. himitsu kaigi, lit. secret meeting)||+。 場にないアクションカード1枚を手札から使用してもよい。使用する場合、+1 アクション。|
|Russian||Конклав (pron. konklav)|
 Secret History