Skipping some that had separate threads...
Confessor
$2 - Treasure
Worth $1
+2 Actions
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While this is in play, you may trash up to two Curses.
+Action makes no sense on a Treasure card, since it is too late in your turn to do anything with the actions. The only effect this has is to increase the value of Diadem by $2.
You cannot just have "while this is in play, you may" on a card, because the card is constantly in play and its effect triggers indefinitely. Existing cards that have "while this is in play" follow it up immediately with ", when you <do X>" so that there is a set trigger condition. (e.g., Goons gives you VP "while this is in play", but only "when you buy a card").
You presumably want the effect to trigger once for each Confessor you play in your Buy phase. That is spelled "when you play this, you may trash up to two Curses from your hand" (it's important to specify sources and destinations of cards, except for buying and gaining).
Helping Hand
$3 - Action-Victory
Reveal your hand. If you have no Treasure cards or only one Copper, gain a Gold and put it into your hand.
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Worth 2VP
This could be really powerful. I assume you used Tunnel as a reference point for pricing this. I'm not sure that "if you have no Treasure cards or only one Copper" is as hard to arrange as "when you discard this other than during your cleanup phase". Also you're getting the money in hand, which is a huge difference. But then, this is a terminal Action, and when you get that money in hand, you still only have at most $4 in hand. The other obvious comparison is to Explorer; this is much cheaper and also worth VP, but it can't get you Silver and its Gold is harder to get. I can see this doing some interesting things in engines (although it can't be TRd/KCd).
Patron of Arts
$5 - Treasure
Worth $0
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When you buy a card, you may gain a card costing up to $5 that has a different color banner than any cards gained this turn.
"Banner colour" is a weird criterion. Usually you talk about card types instead. Also, some cards have multiple colours in the banner. And I have no idea how the card name relates to the card effect.
Pied Piper
$3 - Action-Attack
+1 Card
+1 Buy
Each other player discards the top card from his deck. You gain +$1 for each Treasure discarded in this way.
This isn't an Attack, for the same reason Tribute isn't. I suspect it scales too well in multi-player games. Again I have no idea how the card name relates to the card effect. (I kinda expect a card named "Pied Piper" to have an obvious synergy with Rats...)
Sculptor
$4 - Action
+$2
Look at the top 4 cards of your deck. Put two of them into your hand, discard the others.
+2 Cards and +$2 is already (a) a not ordinarily done combination; (b) really strong. And this is that, plus some sifting.
During the set design contest, the following card was put forward: "+2 Cards, +$2, Discard 2 cards." It got few votes because it was pretty bland. Its author priced it at $5, and people were talking about how this is actually the proper price for such a card because the effect is very powerful. The combination of coin and sifting is very easy to underestimate; it's huge in BM decks.
Cudgel
$5 - Action-Attack
+2 Cards
+$2
Each other player draws one card, then chooses one: Discard two cards, trash a Treasure that is not a Copper, or gain a Curse.
The vanilla bonus here is quite a lot. See notes on Sculptor. I think that already makes a viable $5 card.
The attack is interesting (like Torturer, but with more options, and with the Curse not going in hand), but the combination is far too much.
Savoyard
$3 - Treasure
Worth $1
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When this is in play, it is worth an additional $1 for each other Savoyard you have in play.
So... like Bank, but it only considers other copies of itself, instead of all Treasure. The strange thing is that while Bank is a $7 card, this is actually really really weak; if you line up
three of them, then they're still only as good as the three Silvers you could have bought instead. Compared to Fool's Gold, this is dead in the water. And honestly I think Fool's Gold already has this design space pretty well covered. Although, if you made the vanilla bonus $2 and bumped the cost to $5, I might start thinking about it more seriously...