Additional Rules from the Rulebook
The gained card goes into your Discard pile. It has to be a card from the Supply. You cannot use coins from Treasures or previous Actions (like the Market) to increase the cost of the card that you gain. If you use Throne Room on Feast, you will gain two cards, even though you can only trash Feast once. Gaining the card isn't contingent on trashing Feast; they're just two things that the card tries to make you do.
The Secret History of Feast
In an article on Board Game Geek, Donald X. Vaccarino commented on the development of Feast:
- At one point the 1st expansion had a "one-shot" theme. I eventually realized that that was a bad theme because some players don't like those cards. They don't like how the card doesn't stay in their deck, or something. I'm not too clear on it but I know there are haters out there. So I split that theme up, with some of the cards going into limbo. One-shots are different enough that I think they're worth doing sometimes, and well some people like them fine. But I might not even do one per set. The main set got this one as it's the least offensive; you do get to hold onto the card you fetch with it.