Cards that resolve other cards are one thing, but what happens with cost reducing effects when using royal linage? I play RL, I choose Bridge. Now I want to play a Laboratory. Is that more expensive than Bridge? It costs 4$. Bride costs 3$, but it used to cost 4$ when I played it. I guess for each card you compare the costs at the point of play, so when I want to play Lab, I compare it to the bridge that I just played. That bridge now costs 3$, so I can play Lab. Is that how you intended it to work?
I think its pretty clear that you compare the current costs, not the costs when you played the card.
I would try to find a version that works with "play this again," instead of "repeat any number of times." I'm not sure this is a phrase that should be on a dominion card.
Do you have an argument as to why "repeat any number of times" is a bad phrase to be in a card? BTW, your proposed phrasing does not work because it draws after playing instead of before, which is a lot worse. And I find it way more confusing than "repeat any number of times". We already have "repeat any number of times" kind of things going on with multiple revelations of Reactions.
Birthright - Action - Reaction - $4
+1 Action
Put all the cards from your Birthright mat into your hand.
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When you would gain a card, or discard a card from your hand, you may reveal this from your hand. If you do,
set that card aside on your Birthright mat.
Would gain does not work, because you do gain the card anyway.
It seems crazy powerful with things like warehouse. Play warehouse, draw 3 cards; if one of them (or one of the cards in your original hand) is a Birthright, the -3 card disadvantage becomes nonexistent. that goes for all following warehouses too, so all you have to do is buy tons of warehouses and a couple of Birthrights. I'm not sure if that's a problem, it just means there are some really strong combos, but my gut says that it's not good. Sifting is already strong, a card that skyrockets the usage of sifting seems... unnecessary? I get the feeling that you didn't design the card with that aspect primarily in mind, but it's the main power of the card. I would probably try a version that reacts only go cards gained.
Ok, this may be a too strong combo... its not that easy to pull it off, beause you can only withold playing it for so long, but the fact that you do not need the BR in hand to start (and that you can afford playing Warehouse and fail, as long as oyu eventually start drawing) makes it way easier than Village+Smithy.
PPE a lot
What does this mean? Google did not clarify it to me (lots of acronyms are PPE apparently).
OK, probably the card is still too strong just for its ability to set aside all your Victory cards as you gain them. If you want to push the aspect where you remove the cards from the mat, you might want to not allow Victory cards to be set aside this way.
There is this card from one
mini-set design contest:
Astrolabe by popsofctown
$4 - Treasure
+$1
--
While this is in play, when you gain a card, you may set that card aside. Return it to your deck at the end of the game.
This is weaker to just set aside Victory cards because it does not provide money. In the playtesting thread, they say its weak more than strong. And of course, it is flexible but it does not work for everything at once because you need to put all the cards in your hand, not just a few.
To avoid it being to strong I want to limit the number of cards you can retrieve. It will also make it more different than NV as a megaturn enabler. And I will make it a stack to make it more difficult to use it to avoid discarding and setting VP aside at the same time. How does this look?
Birthright - Action/Reaction - $4
+1 Action
Put the top 3 cards from you Birthright stack into your hand.
---
When you gain or discard a card other than during your clean-up phase, you can reveal this from your hand. If you do,
set that card aside on top of your Birthright stack.
So, Warehouse+Birthright nets you less than Village/Smithy would, but it is easier to pull it off, and you can mix-and-match drawing and sifting as well (you do not need to reveal BR to every discarded card). And of course, you have the tricks with BR to set aside your green and use Warehouse or other sifter as pseudo-trash. LF, do you still think its too good for the setting aside of green? I think its pretty good, but it is not like it is turning off other strategies, just making your engine not-choke and a lot more viable. You do need to build the engine and decide when to add a card you only need for greening. I don't think its a better enabler for engines than Chapel, possibly even less than Steward or Remake, because it does not accelerate you early game (barring combos with sifters).
EDIT: I also like the stack idea because it is more original.