(GPT-3 is OpenAI's gigantic 175 billion parameter language model. It's a neural network that predicts the next word in a sequence of previous words.)
I
once posted a bunch of GPT-2 generated cards in the Really Bad Card Ideas thread. But those were (a) generated with GPT-2 (which is much smaller than GPT-3) and (b) I only had access through a small prompt that barely had enough space to show it two current cards. The proper way would have been to train it on a large corpus of cards, but I couldn't do that.
Now, on the other hand, I'm using
AI Dungeon. I can show it much more cards, and the results are far more impressive than they used to be. I structrured the entire thing as a conversation between an "Interviewer" and "Donald X." The Interviewer asks questions about Dominion, Donald X answers, he shows some of the existing cards, and then some new cards.
This way, I can also request particular types of cards. I'll use this thread to catalog the good ones.
Victory Cards
Yards – Victory – 6$
Worth 2VP for every 10 cards in your deck (round down).
Stronghold – Victory – 10$
Worth 3VP for every 10 cards in your deck (round down).
County – Victory – 6$
Worth 2VP for every 3 Silvers in your deck (round down).
Highlands – Victory – 5$
Worth 1VP for every 5 Treasure cards in your deck (round down).
Attack Cards
Inquisition – Action – Attack – 5$
Each other player reveals their hand and trashes a revealed Action card costing up to 4$. You gain the trashed cards.
Begging – Action – Attack – 2$
Gain 1VP for each Treasure card in your hand. Each other player reveals their hand and trashes a revealed Treasure card costing up to 4$. You gain the trashed cards.
Mutiny – Action – Attack – 4$
Each other player reveals their hand and trashes a revealed Attack card costing up to 5$. You gain the trashed cards.
Villages
Swamp Village – Action – 3$
+1 Card
+2 Actions
+1 Buy
Trash this to gain a card costing up to 4$.
Sea Village – Action – 3$
+1 Card
+2 Actions
You may reveal a Treasure card from your hand. If you do, gain a Silver.
Papermaker's Village – Action – 2$
+1 Buy
+2 Actions
You may reveal a card with Papermaker in its name from your hand. If you do, gain a Silver.
Smelting Village – Action – 2$
+1 Buy
+2 Actions
Trash a card from your hand. If you do, gain a Coin token.
Silk Dyer's Village – Action – 3$
+1 Buy
+2 Actions
Discard any number of cards. +1 Card per card discarded.
Mobilized Village – Action – 5$
+2 Actions
If you have two or more Villages in play, +4 Actions.
Others
Equipment Stash – Action – 2$
+2 Actions
Look through your discard pile and put a card from it into your hand. If you do, put Equipment Stash on top of your deck.
Bag Lady – Action – 3$
Trash this or a Treasure card from your hand. Gain a card costing up to 2$ more than the trashed card.
Miscellaneous
Royal Escort – Action – Reaction – 5$
When you would lose the game, you may reveal this from your hand to ignore that loss.
Marauder – Action – Attack – 2$
Trash this card and another card from your hand. Gain a card costing up to 2 Coins less than the trashed card.
(Lol'd because this is probably a better card than ErrinF's card that trashed itself and another card and had potion in its cost.)
Tornado – Action – Reaction – 6$
Trash this and all the cards in your hand and gain a Gold, 2 Provinces and a Curse.
Feast – Action – 4$
You may eat a food this turn. Draw until you have 5 cards in hand. You may eat another food.
Royal Blacksmith – Action – 5$
Trash this card. Gain a card costing up to $4.
King's Court – Action – 10$
Gain a Prize card.
Wood Village – Action – 3$
+1 Card
Gain another Village.
Lumbermill – Action – 4$
+1 Card
+2 Actions
You may trash this to gain a Wood token.
Salted Pork Village – Action – 2$
+1 Buy
You may discard any number of cards. Gain a Food token for each card you just discarded.
(What's with the food tokens 
maybe an import from MTG.)
Bakery Village – Action – 4$
+1 Buy
+2 Actions
You may reveal a Bread or Pie token from your hand. If you do, gain a Baking Token.OuttakesAfter a few minutes of swooning and praising Donald, you snap out of it just in time to hear him (and the rest of the crowd) yell "SOYLENT GREEN IS PEOPLE!" Whatever that means
