Time for the obligatory text-dump. Then I'll post a "secret-history".
Aphrodite
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So it's a Monument bank, with a crazy cost and wacky type-changing mechanics. This card feels like a trap; "Man, if I get a lot of these $9 card, golly--you are in for it now!" This card is too slow for Colony games, much less normal ones.
Bacchus
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So uh, this applies during Cleanup (whether intended or not), so it's basically "skip a turn, get 5 VP." Which is simultaneously incredibly lame and overpowered.
Let's assume it doesn't work that way. So this card does nothing on boards without a draw engine? And it makes cantrips kinda sort terrible? And it's terminality clashes sharply with everything you would ever want to play it with? This just doesn't work like anyone wants it to.
Ceres
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What a curious, attractive, and obviously well-tested card.
Demeter
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I've done a lot of testing with alternative Victory Point stuff, and I can tell you immediately that this is way too exponential, way too fast. All competing strategies can't compete with this; I buy 6 of these with 10 Curses and hey that's 110 VP. 4 with 6 curses is already 42 VP. That's 4 $6 cards, matching 7 Provinces. All other victory conditions are made obsolete.
It's a good design in isolation but way too good as currently formulated. I also dislike how exclusionary it is to all other strategies; even Fool's Gold tolerates other cards way more than this.
Playtest!
Epona
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Simple enough. A flexible opening--Village greatest hits? I was going to say it's interesting, except it isn't. But that's okay! Contrary to popular belief, the point of cards is not to be interesting, but to make Dominion a fun game. This Village, like Pawn, contributes modestly to that.
It might be best to think of this card as an alternative, mostly superior Silver. I bet it would be bought by winning decks at a rate even higher than Fishing village. I'm a tad worried that such a flexible, potent Village would have a negative impact on the Action economy.
Fortuna
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Targetted attack, super political, requires all Treasure playing to be one-at-a-time with awkward mindgame consequences. This sort of gameplay might be interesting in a 2-player game built entirely around it, but it's totally foreign to Dominion.
Did I mention it's a targetted attack? Do not pass Go, ect.
Glycon
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Okay so, I like the idea a lot, but man. While I haven't playtested it, this just seems like it would be absurd. Market for $2? Market might be the single card that would be most broken at $2; an economic cantrip with +Buy? Never hurts in any quantity and enables bulk buying of 2s.
So every game people buy as many of these as they dare, and then wait to see who takes a leak in the punch bowl. In a 2 player game, I don't know if I see this happening? You buy 4, maybe 5 or 6 if they are uncontested, and neither side has much incentive to invest in hurting you both equally. So we're all just playing this game with bonus Markets. Hm.
It's pretty political in 3-4 player, or at least can be in a non-trivial number of games.
You could word it like an inverted City to clean it up, maybe. Is discard a card at 1 empty pile really needed? Also, how much does it hurt the card if you take away the +Buy so it doesn't feed itself in a really demanding way? I mean, cantrip +$1 for $2 is still biscuits and gravy.
As it stands, this makes 2/5 really strong. I'd buy this at $3 for sure.
There's a really good design going on here, but I think it's facing some non-trivial development hurdles.
Hermes
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I have two reactions to this. "This is interesting." and "Oh God no, please no." Like, has this been playtested? I can't imagine it being fun, in 80% of games you are just going to have this obnoxious lame duck phase tacked on.
Iris
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Why isn't this an Attack? This is a really, really obnoxious card with Minion. It's basically a better Militia for $3... Obnoxious opening implicaitons. The fact that it can hit you is odd since it normally won't apply, and when it does it will often be trivial?
Jupiter
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Basic, elegant, and almost cute. Dual-purpose modest trasher and basic village, at a fair price. It's one of the best Villages as it stands, but maybe that's okay?
I do have one gripe though. Non-terminal trashing, especially early, is a non-decision. Normally the pursuit of trashing has certain implications, both buying the trasher and playing it has an opportunity cost and thus they add interesting decisions to the game. (Upgrade achieves smilar by being a different kind of trasher, and being a powerful expensive card competiting with other powerful expensive cards.) This card bypasses most trashing decision-making.
Why not "when you gain this"? It makes the card marginally stronger, but who cares. It allows cute combos and I see no reason not to.
Kratos
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Whoa! Now I like crazy and bold, but this might be crossing the line. It's cute with trashers and dangerously powerful with drawers, but attacks are where this really gets in trouble. Like, just look at Witch, Torturer, or something cheap like Masquerade. Abolishing the Action economy is just too significant here, way too many boards are going to degenerate. It's very centralizing, like a certain other $7--but King's Court gets away with it because it's less consistent and thus takes a little longer to hit critical mass.
I feel like this card should get some alternate award, like "Most Crazy". It made me think pretty hard about the implications, more than any other!
Luna
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Interesting. Modestly powerful but mostly end-game; seemingly cost well. The only hang-up is that a lot of the decision making it creates isn't really compelling; discard something I'd like to play, for an economically decent reward? Compare that to Salvager, where the stakes are way higher and the decisions are thus more awesome. Helping the winners win more (even more than most cards) is also kinda annoying. Still, good.
Minerva
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This is good but I feel I'd want to playtest it. I'm worried about the end-game power, but appreciate that the set-aside mechanic is covering the crazy cases. It's just so powerful late game, in spite of being decent early game.
It's slightly unclear, as worded, if "otherwise gain as Estate" refers to not electing to set aside a Victory card, setting aside one that isn't an Estate/Duchy/Province, or both.
Nox
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Let's see... Targetted, political attack? Anti-fun mechanic? Really nasty implications with Gold? Your own attack hits you twice? Really silly degenerate cases involving Copper? I elect to Nox Nox, forever.
This is why we playtest things!
Osiris
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So this is really interesting, but a big concern; getting into an Osiris war is an indefinite game state. So red flags go up before I can even start to analyze this. Why not trash it, why does it have to go back to the Supply?
As a $0 no-benefit terminal, this is kinda uninspiring. Why not make it $2-4 and give it a modest benefit, so people get at least somewhat excited about it and start fighting over it?
Pluto
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I like this, but suspect it isn't very good as stands. "Lab for everyone" is not something I'd ever pay for, sans Militia/Ghost Ship/Possession shenanigans. The option to give everyone a Lab to give yourself a Village is pretty dubious, but I guess it can't hurt.
This could cost $2 and it'd be fine; still weak and usually unattractive, actually. I like the premise and it's elegant as stands, but it needs to offer some more concrete relative benefit.
Quirinus
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Super Thief! Problem is, I don't like Thief. This card is less dubious--it clogs your enemy's deck rather than thin it. But uh, how fun is that? Thief games are, for all their faults, wet and wild, willy and wacky. Everyone's deck is thinned of Copper, and you start throwing good Treasures around! Here everyone just sits around with their increasingly bloated Copper decks. Since Quirinus is afforable with Copper-based decks, and the money it provides is a small defense against itself, so hey guess what everyone is gonna be buying more of. This just doesn't sound fun, regardless of the card's power level.
Roma
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So we've got a big set of effects that I don't really care about.
-Discard a victory card, okay great, but gain a cheaper Victory card? On top of my deck? Ew. And I have to do this?
-Discard an action, ew. Why would I want to do that? Actions are for having fun! Playing a $5 card to discard an action you don't want to gain a Silver is not exciting.
-Discard a Treasure, alright I better get something awesome. Curse attack? Wait, Witch does this except you get +2 Cards; here I have to discard a treasure? Weak!
-Discard a curse to draw +1 Card and give out Coppers? Again, how is this not a terrible version of Witch?
The effects aren't fun and the cost is way off. I wouldn't buy this card as written at $4.
Sol
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Uh, what. This is silly nonsense; an arms race that leaves us back where we started, but with terrible un-fun decks? A bonus point for comedy at least.
Terra
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Fun alternate draw engine. Problem is, you normally need a surprisingly high critical mass of them to work; 1 out of 3 cards? I mean, to chain you need 2 in your 6 cards. And unlike traditional raw drawing power, the cards you are cycling are going back into the draw source as you reshuffle, so it's diluted. I'd want to playtest this to see just how much slower mid-game it is than Lab.
It's also crazy with TR (and KC) in a fun way Minion could only dream of. Really attack resistant, really trasher dependant. Loves Cellar, Warehouse, SC/Vault, I think I'm starting to warm up to this card, its presence on a board is interesting--even if it's not as cool or elegant as Menagerie... none of these cards are!
Of these cards, the only ones that I could really justify voting for were Epona, Luna, Terra, and Jupiter--the rest either had some cardinal sin, too narrow of a scope, or had some development concerns (and named Glycon). I think I put Jupiter in honorable mention due to the lack of gameplay it brought to the table, Epona in 3rd for being too centralizing, Luna in 2nd by default, and Terra in 1st because it creates more gameplay than Luna.
Time to talk about my card!