This one is mostly for fun, since it massively breaks the whole Dominion theme.
Antarctica
Action-Duration
Cost: 6
+1 VP
If Antarctica is in play during your clean-up phase, do not discard it. Discard Antarctica at the start of your turn. While Antarctica is in play, any player wishing to use an Action must first discard an action card from their hand.
(I considered making this an attack, but... no, Antarctica isn't an attack. Antarctica is just Antarctica. I could see making it a Victory card rather than generating tokens, though. Villages are great against this card: either you get to play an extra action, or you discard the Village to play the action. Alternately, Big Money. But if a 5-action card can be use to beat Big Money, then the choice whether to get Antarctica becomes relevant again... I have doubts about this one, though. Then again, is it really any more of a pain than Goons?)
Extravagant Feast
Action
Cost: 5 (EDIT: Originally, this costed 4, which was OP.)
Trash Extravagant Feast and discard up to three cards from your hand. Gain a card costing at most (4) more than the number of discarded cards.
(After a moment's thought, I realized that "any number of cards" was going to lead to idiotic games where the winner is whoever has enough luck to alternate 4-coin hands with hands that are dead except for this card. I changed the cost from 4 to 5.)
(Holy cow, the version of this that cost 4 was broken. If you buy the 4-cost version early in the game, discarding one card to break even with vanilla Feast is virtually no opportunity cost whatsoever, leading to easy Golds or even Banks wicked early, and you can still buy Silver or an action those turns. Way too good. When it costs 5, then by the time you can actually play it, it may actually be a meaningful decision whether/how many cards to discard. It's still good enough to buy too, but it rapidly becomes obsolete *unless* attack cards are making it difficult to get 6-7 coin hands in a reasonable amount of time. But now that it costs 5, how does it compare to Vault? Well, Extravagant Feast can get you those cool 7-cost cards guaranteed, so that's cool. And if you discard two, you might have spare change to buy a Silver or something that turn, if you really wanted to EF for a Gold or something; it would probably take a few more turns before a Vault in the same turn would likely bump you up to buying a Platinum. So the new version looks like it depends on the board, but typically becomes relevant at a certain point and then ceases to be worth it. But ymmv, only tested it 2-3 times so far.)
Lucky Penny
Treasure - Reaction
Cost: 3
(1)
When you play Lucky Penny, reveal the top card of your deck. Draw it, or return it to the top of your deck.
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If you have a Wishing Well in play during your action phase, you may discard Lucky Penny and return Wishing Well to your hand.
(The reaction effect is an optional feature to include, but... yeah, it belongs, I think. This card is sort of alright even without Wishing Well, but probably not great or an automatic buy. A sort of watered-down Venture that sometimes makes your next turn a little better. Probably too good if it costed 2, not sure.)
(EDIT: This card is really strong, actually, maybe even worth 4, but I don't know. At 3, it's strong when your deck is mostly a mix of green, gold, and/or purple, when it will almost always be doing good things for you every time you see it, acting as either a self-spy or a Venture each time. When there are strong white card combos on the table, then it may be hurting you, but really... that's the only time it's worse than Silver. I really don't know what to do about this card. I like it, but it makes for some really breezy games. It's not broken like 4-cost Extravagant Feast, but it might be a little OP. Also, the test game had Bureaucrat, and I shouldn't really have to explain why that was insanely good... Seriously considering a cost of 4 here. Either that, or it can cost 2 and have an "optional trash-when-played" precondition to the special effect for more drama/strategy. y/n?)