Additional Rules from the Rulebook
When you play this as an Action on your turn, you first discard any number of cards from your hand, then get 1 coin per card you discarded. You may choose to discard zero cards, but then you will get zero additional coins. The other ability does nothing at that time as it is only used as a Reaction. When someone else plays an Attack card, you may reveal Secret Chamber from your hand. If you do, first you draw 2 cards, then you put any 2 cards from your hand on top of your deck (in any order). The cards you put back do not have to be the ones you drew. You can put Secret Chamber itself on top of your deck; it's still in your hand when you reveal it. Revealing Secret Chamber happens prior to resolving what an Attack does to you. For example, if another player plays Thief, you can reveal Secret Chamber, draw 2 cards, put 2 back, and then you resolve getting hit by the Thief. You can reveal Secret Chamber whenever another player plays an Attack card, even if that Attack would not affect you. Also, you can reveal more than one Reaction card in response to an Attack. For example, after revealing the Secret Chamber in response to an Attack and resolving the effect of the Secret Chamber, you can still reveal a Moat to avoid the Attack completely.
The Secret History of Secret Chamber
In an article on Board Game Geek, Donald X. Vaccarino commented on the development of Secret Chamber:
- The set had a reaction early on, but had lost it by the time development started. Dale wanted another reaction, and the set had space, due to going up to 25 cards. I didn't want to just stop attacks flat-out again, so this card instead does something odd that's useful against lots of attacks. You'll have to consider the individual cases for yourself, but really, it does show a lot of attacks what for. The non-reaction part had been a card in the main set in the murky past, which had left due to being too weak. It seemed good enough here with the reaction tacked onto it, and cute because it helps vs. Curses, which the reaction part doesn't. As with the similar nixed card described in the Courtyard entry, this can cause some AP, but it's not as bad because the attack gives you some direction and it isn't your turn.