Right, so you mention Knights as inspiration, so I assume that this is meant to be a single pile of different cards, like Knights. Right off the bat, I'm seeing some dangerous design assumptions.
Now I focus on interesting ideas, balance would be second concern. Like in knights I want upto two cards awesome so buying other is risky proposition.
It's great to focus on interesting concepts first, but you do still need to think about balance. Most of the cards in your first version look way too powerful.
You also talk about having a couple extra powerful cards so that it is risky to buy them, lest you reveal a better option for your opponent. This exists to some extent with Knights, but the variance in their power is not
that big. The key thing is that every Knight still has the same attack. Yeah, sometimes you may get Anna and have the only trashing on the board, or you might get Martin for the only +Buy. But overall, the power levels aren't that disparate. Also note that you can counter the opponent's awesome Knight with a weaker Knight, because Knights trash each other.
With your Citadels stack, all the cards are extremely different. Depending on the board, the power of the different cards will vary wildly. Moreover, the cards are so complex and different from each other that it is difficult to remember what the possibilities are. With Knights, they all have the same attack and their special bonuses are all very simple. +2 cards, +$2, +2 Buys, +2 actions, cantrip, gain a card (costing up to $3), trash up to 2 cards, discard attack, 2VP, gain Gold on trash. I can easily name all those by memory because they are all very simple.
Four other overall critiques:
- If you have different cards in one stack, you should probably give them a unique type to indicate that they go together. This is done with Knights and Ruins.
- Some of your cards refer to other cards that might not even be in the kingdom. That's something that should probably be avoided.
- Your wording is not consistent with official Dominion cards. I recommend looking up official cards that are similar to yours to get a good idea of how they should be phrased. Dominion cards are pretty consistent, and fan cards should strive to maintain that consistency and clarity when possible.
- If I'm counting correctly, you only have 8 cards here. There should be 12 when playing with more than 2 players. Not a huge deal though; you can just say it's something special about this particular set of cards, like Rats.
assassin 5$
action-attack-victory
Each other player gains curse on top of their deck
and if he has 5 or more cards he reveals their hand
and puts a card you choose on top of their deck.
worth 1vp per curse in deck of opponent on your left.
In a game with no other cursing, Assassin will absolutely dominate. For that alone, it is too powerful. Consider how strong Followers is in the same situation. Now consider how much more work is needed to actually get Followers. All it takes to get Assassin is for it to be on top of the stack.
The second attack is just as brutal. Pillage is so strong that it trashes itself. Top-decking means that you can more creatively harm your opponents than with Pillage. If you play this when their hand is weak anyway, you can still top-deck junk to hurt their next turn!
silverspawn brought up the Sea Hag clause. It's not as important on this card because there will only ever be one copy of it. Even so, it may be worth adding in the clause to prevent shenanigans with King's Court. That said, it's probably better to remove the cursing altogether (because it is just too dominating if it is the only curser in the kingdom).
silverspawn also mentioned the problem of not producing resources. This is actually not a huge issue, but it's something to keep in mind. Playtesting always showed that many players don't enjoy cards that don't provide personal bonuses. Still, there are some official cards like this (Sea Hag, Saboteur, Sir Michael).
Don't know how to feel about the VP per opponent's Curse.
Master thief 5$
action-attack-victory
Opponents trash a treasure card from your hand
or reveal hand with no treasure. You may gain any
trashed cards, putting them in hand.
worth 1vp per gold in your deck.
This should say "from
their hand", right?
So this is a Thief that steals from their hand directly into your own. This does worry me a bit, but I think it's OK to start playtesting.
Since this has the opponents choose from their own hand, the treasure trashing is usually weaker than Thief. Thief can sting when it gets lucky and finds a good Treasure, but opponents would have to have much worse luck if they get stuck in a position where they have to give up a Platinum. Players should hesitate to trash down to nothing but Platinum against Thief, and they should similarly hesitate against Master Thief.
This attack is bolstered by also having a Cutpurse effect that works on more than just Copper. That's the part that worries me more.
Finally, the ability to gain ALL of the trashed cards might be too powerful. Dominion is not strictly a 2 player game. Though many of us prefer the head-to-head game, you also have to consider how strong a card is with 3-4 players. But that said, this particular effect of Master Thief might never amount to more than Beggar's on-play. So maybe it would be alright after all.
So all that feels a little iffy, but it's not too crazy.
Don't know how to feel about the VP for Gold.
magician 5$
action-victory
Everybody discards their hand. You draw a card
for each card that player on your left discarded.
Each other player draws a card for each card that
you discarded but at least three cards.
worth 1vp per potion in your deck.
Definitely need to clean up the wording here...
This is an attack so it needs the attack type. You are forcing players to discard and re-draw, and they will usually draw fewer cards than they started with.
Usually, you will be discarding and drawing back up to 5 cards. If you play it smart, you will put everyone else down to 3 random cards. Even if you played this from a 5 card hand, you will only have 4 cards left to discard so the attack is as powerful as Minion. But if you can play a few other cards first and reduce your hand-size, this is brutal. Minion is painful because 4 random cards is usually weaker than the best 3 of 5 that Militia causes. Magician can put everybody else at 3 random cards which is very, very harsh.
The VP per Potion is not a good idea. Potions might not even be available to purchase. Even if they were, you might not otherwise want to buy a Potion card. Even if you do, it's very rare for you to want more than 1. VP per Potion is thus superfluous most of the time.
beggar king 5$
action-victory.
Gain 4 coppers putting them in your hand.
Worth 1vp per a treasure in your deck.
What do you mean by "per a treasure"? If you mean that it's worth 1VP for each copy of one treasure of your choice, then that is way too powerful. It's more than a Province if you don't trash starting Copper, and it's easy to boost that further (including the on-play effect essentially adding +4VP).
If you mean, "per differently named treasure", then it sounds more reasonable.
archbishop 5$
action-duration-victory
Gain a coin for each reaction card in play.
If opponent plays attack you may reveal this;
if you do you are unaffected by attack.
While this is in play you are unaffected by attacks.
worth 2vp per chapel in your deck.
First, this should be a reaction since you allow it to act as a Moat.
Second, for this to work as a Duration, it needs to have an effect on the next turn. Otherwise, it will be cleaned up immediately and never remain in play.
Counting reactions in play is extremely niche. Not every board has a Reaction available, several reactions can't ever be in play (Hovel, Tunnel, Fool's Gold -- at least not during the action phase), and all the action-reactions are terminal which makes it tougher to get them into play before Archbishop. So Archbishop will usually just be +$1. Not that compelling.
The 2VP per Chapel is really weird. Chapel might not even be in the game! If it is, there is almost never a reason to get a second Chapel, so Archbishop essentially makes Chapel into a super-Estate. Usually not that interesting, but still with a lot of potential in the late game (e.g. Tunnel is still purchased even without the possibility of discarding). Giving only one player access to that significant amount of alt VP is really imbalanced.
merchant 5$
action-victory
+1$
Choose one: Draw two cards or gain two gold.
worth 1vp per a coin token.
Freely gaining two Gold is really powerful...
VP per coin token does not work well. There are only 5 cards that produce coin tokens so they will be absent most of the time, especially if the player doesn't own Guilds. If coin tokens are available, this is too valuable. Note that there are no non-terminal cards that give VP tokens. On the other hand, there are 3 non-terminal coin token cards, one of which only costs $2. Butcher gives two coin tokens at a time. Merchant Guild becomes similar to Goons. If you have Merchant, coin token cards become a LOT more powerful for you than for your opponents.
architect
action-victory
+ 1 action
+ 2 buys
+ 2 cards
worth 1vp per 3 cards in your deck.
Strictly superior to Laboratory, even without the VP.
But the VP potential here is enormous! This is worth more than 3 Gardens and it isn't even a dead card in your deck. Far from it, it actually provides you +2 Buys to further bloat your deck. That's far too powerful.
warlord 5$
action - victory
+1 buy
+1$
When you buy a card return it in supply. Choose a opponent.
He reveals top three cards from top of his deck and
trashes card any copy of card you returned.
worth 1vp per duration card in your deck.
"Choose an opponent to attack" is deliberately avoided in Dominion. If you like the politics, go for it, but this will always be something that is criticized here.
Now, if it affected everybody, it's not that bad. The issue is that it is extremely swingy. Maybe you do it with Province and your opponents trash 3 Provinces. That is a very cost-effective pay-off. Or maybe you completely whiff and waste your buy for nothing.
The VP per duration card is useless in games without durations but way too much in games with good durations like Fishing Village or Wharf.
Overall, you really do need to give some thought to the balance of the cards. Think through how it would actually play. Since you are doing a Knights-like stack with Victory cards, consider the impact of only one player getting that card.