Additional Rules from the Rulebook
You pick another Action card in your hand, play it, and play it again. The second use of the Action card doesn't use up any extra Actions you have. You completely resolve playing the Action the first time before playing it the second time. If you Throne Room a Throne Room, you play an Action, doing it twice, and then play another Action and do it twice; you do not resolve an Action four times. If you Throne Room a card that gives you +1 Action, such as Market, you will end up with 2 Actions left afterwards, which is tricky, because if you'd just played Market twice you'd only have 1 Action left afterwards. Remember to count the number of Actions you have remaining out loud to keep from getting confused! You cannot play any other Actions in between playing the Throne Roomed Action twice.
The Secret History of Throne Room
In an article on Board Game Geek, Donald X. Vaccarino commented on the development of Throne Room:
- For most of its life this card cost 3. My feeling was that you didn't want to buy two on turns 1 and 2, and probably didn't want to buy one on either of those turns (except with the Feast combo). Later in the game it doesn't matter as much whether it costs 3 or 4. So why not 3? In general, if a card can be cheaper, I make it cheaper. I want the cards as cheap as possible without breaking the game, rather than as expensive as possible without going unplayed. So, I knew Throne Room was good, but it seemed like 3 was okay.