Thank you for all the submissions! As usual, you produced a lot of interesting ideas, and deciding was hard. I will go through the cards in alphabetical order.
Breeder by Commodore Chuckles
Breeder
$4 - Action
Heirloom: Pasture
+1 Action
Reveal the top 2 cards of your deck. If one has a type that the other does not, put them both into your hand. Otherwise, put one in your hand and the other back.
I am not sure why this was paired with Pasture. It makes it weaker than it would be otherwise, and this is already a kind of weak card. It also doesn't really give an incentive to keep Estates around.
City Farm by Gazbag
City Farm
$5 - Action
Heirloom: Goat
+1 Card
+2 Actions
Count your deck and discard pile. If there are 10 or fewer cards total between them, +1 Card.
I like that this gives extra draw that's hard to use. There is an interesting push-pull mechanic where the more easily you can activate this, the less likely you need it. It may be a bit too powerful in the early/mid game as with Goat, it takes a while for your deck to grow.
Collector by scolapasta
Collector
$4 - Action
Heirloom: Magic Lamp
+1 Action
At the end of your turn (after drawing), trash a card you set aside with Collector and gain a card costing exactly $1 more than it. Discard the rest.
-
While this is in play, when you play a non-Duration card, you may set it aside.
I feel like this is just a more complicated version of Improve? It is a bit more flexible, but on the other hand the on-play effect is weaker. Also this does not ensure that 6 different cards can be play in a turn, which I think a card that has Magic Lamp as its Heirloom should.
Construct by artless
Construct
$3 - Event
Heirloom: Pouch
Until the end of this turn, when you buy a card costing $3 to $6, gain a copy of it.
This is like a more straightforward version of Talisman/Stonemason. I think it will too often be automatic and not create interesting decisions.
Drawbridge by NoMoreFun
Drawbridge
Night/Duration - $4
Heirloom: Pouch
From the top of your deck, set-aside (face down) a card, plus another card per unused Buy. At the start of your next turn, put the set-aside cards into your hand.
-
This is gained to your hand (instead of your discard pile).
This has a fairly broad range in terms of how useful it will be... there are cards that give you abundant buy (Workers' Village) and other times it's harder to come buy. This is somewhat offset by the fact that when you have lots of buys, you likely won't have a lot of cards left in your draw pile. That makes it feel overall more balanced. My only concern is that it might be too strong to just be able to set aside this turn's buys in a deck-drawing engine.
Friar by Fragasnap
Friar
$2 - Action
Heirloom: Pasture
Trash a card from your hand. If it costs at least $3, gain a Duchy and an Estate. Otherwise, gain 2 Estates.
I have a hard time judging the usefulness of this. Feels like there is a very small window near the endgame when you would prefer this over nothing and over Estate. I'm not sure it has enough of an impact to make Pasture matter.
Gallery by Gubump
Gallery
$8 - Project
Heirloom: Lucky Coin
During your turn, when you play a Silver, +1$
This is pretty expensive compared to Training. I think a lot of the time, you'd prefer a Province, as with lots of Silvers in your deck, you're already in good shape for buying Provinces. It may hav a place for when you struggle to hit $8 due to discard attacks, but then again, when you struggle to hit $8, you'll have a hard time buying this.
Gambler by spineflu
Gambler
$4 - Action
Heirloom: Lucky Coin
+1 Buy
+2$
When you play this, reveal the top two cards of your deck. If the revealed cards cost less than $7 total, reveal either 1 or 2 more cards. If all the revealed cards cost exactly $7 total, +3$ and trash a card revealed this way. Otherwise, put your deck into your discard pile. Discard all cards revealed by this card.
First of all I think all costs should specify "in coins" to make this not be completely pointless with Debt/Potions. It#s a bit too random for my taste, I wish there was more you could do to influence the outcome rather than just deciding 1 vs 2 extra cards. You could also cut down on text by just saying "Reveal the top 2 cards of your deck. Reveal up to 2 more cards. If all..." Finally, I'm not sure what the putting your deck in your discard does for this, it just seems unnecessarily complicated.
Goblin by majiponi
Goblin
$4 - Action
Heirloom: Poach
+$2
This turn, cards cost $1 less per a card you bought, but not less than $2.
I think it has been pointed out that this interacts weirdsly with cards costing less than $0. It also interacts weirdly with other cost-reducers. While generally I think pairing cost reducers with Puch is smart, I wish this just had the standard "not less than $0".
Kelpie by mail-mi
Kelpie
$4 - Action/Reaction
Heirloom: Cursed Gold
+1 Card
+1 Action
+1 Buy
You may discard any number of Curses for +$1 each.
----
When you gain a Curse, you may reveal then discard this from your hand, to return up to 2 cards from your hand to the supply
I think this is a very nice fit for Cursed Gold. Usually cards that do things with Curses are problematic since you have to add a mechainic that makes you want to gain Curses without them being super strong. But here, Cursed Gold already takes care of this. The extra Buy is nice for Cursed Gold's extra cash. It's also good that the reaction, while still usable when you are attacked with a Curser, it quite costly then so it doesn't discourage going for those attacks too much.
Liminal Arch by Kudasai
Liminal Arch
$6 - Night/Victory
Heirloom: Lucky Coin
If the number of Actions and the number of Treasures you have in play are the same, +1 VP per Action/Treasure pair you have in play.
-
2 VP
I really like the concept here, but I think you want to have a way for this to move the game towards ending. Could be making to play effect on-gain, or draining some other pile, or it trashing something that you played in order to work.
Manor by math
Manor
$5 - Action
Heirloom: Haunted Mirror
+1 Card
+1 Action
If this is the first time you played a Manor this turn, you may trash a card from your hand.
-
When you gain this, gain another Manor (that doesn't come with another).
Feels a bit swingy; when you collide them in a shuffle, that will be a setback. You could trash Hautned Mirror on a collision, offsetting this somewhat, but you need to have it in hand (and Gost isn't so strong that this is always a good thing). Other than that the design is neat and simple.
Meadow by King Leon
Meadow
$2 - Action
Heirloom: Goat
You may gain a Meadow. If you didn’t: +1 Card +1 Action
-
When you trash this, +3 Coffers
I like having the on-trash effect paired with Goat, but I think this is too automatic. When you have $2, it's never bad to get this, and often it's going to be pretty useful. I think this want to be either more expensive or not a cantrip.
Metal Scrapper by anordinaryman
Metal Scrapper
$3 - Action
Heirloom: Lucky Coin
+1$
Trash a non-Victory card from your hand. If it costs $2 or more, choose one: +2 Coffers, or +2 buys and this turn, non-Victory cards (everywhere) cost $1 more.
Comparing this trash Silver for benefit effect to something like Catapult, it's a bit underwhelming. Not sure I'd want the get additional Silvers just for this. Also, the cost increase is a wonky mechanic with some rules confusion and since it's not central to this card, I would prefer if it wasn't there.
Modeller by Aquila
Modeller
$4 - Night
Heirloom: Goat
Name a card you've trashed a copy of this turn. Gain a non-Victory card costing up to $2 more than it.
Fun little Workshop/Remodel variant. I like it. Not sure how much it is hurt by not being able to gain Provinces, but that's probably a good move as with that, it would definitely be too strong.
Night Worker by segura
Night Worker
$5 - Night
Heirloom: Pouch
For each card you have gained this turn, if it is...
an Action card, +1 Villager
a Treasure card, +1 Coffers
a Victory card, +1 VP
-
This is gained to your hand (instead of your discard pile).
Passing up an Iron theme, huh? I'm not sure this needed to have Pouch to be interesting. The most useful option a lot of the time is going to be the Villagers, and I feel that it's a bit too good here? Like 2 of those should solve all your problems in a decent engine. Also being a Night card it's odd that it does not provide a benefit for gained Night cards.
Shrunken Lamp by grrgrrgrr
Shrunken Lamp
$3 - Project
Heirloom: Magic Lamp
When you play Magic Lamp, if there are at least 4 cards you have exactly one copy of in play, trash it. If you do, gain 2 Wishes from the Wish pile. (you no longer gain 3 Wishes)
I don't quite like that ths solely revolves around an Heirloom, and my least favorite Heirloom at that. I also don't like that this effectively harms you if you do manage to line up 6 uniques after buying it.
Silversmith by 4est
Silversmith
$4 - Action
Heirloom: Lucky Coin
+2 Cards
+1 Buy
-
While this is in play, when you play a Silver, you may play it again. If you do, trash it.
Basically turning Silvers into super-Spoils. I think it's going to be too strong, especially with other mid-turn Silver gainers. Maybe try it at $5?
Tropical Island by naitchman
Tropical Island
$5 - Action/Victory
Heirloom: Pasture
You may put this or a card from you hand onto your Island mat.
I don't think this needs Pasture at all. Also I think there's a good reason Island is hard to use as otherwise greening would be too easy. I'm not a fan of this one, sorry.
My final verdict is:
Runners-up: City Farm by Gazbag, Modeller by Aquila, Drawbridge by NoMoreFun
Winner: Kelpie by mail-mi