# How many cards can I gain in a buy phase with a single buy?

I was playing dominion this afternoon and I gained 4 cards during my buy phase with a single buy1, this was pretty impressive, however this got me wondering: What is the theoretical limit to how many cards can be gained with a single buy?

Some ground rules to further clarify what I mean:

• Only cards gained during the buy phase count.

• As suggested by Joe W and GendoIkari only cards gained after you purchase something count. (for example using loans to discard tunnels doesn't count as gaining)

• You may only use one buy even if you have more.

• We only count cards that are kept until the end of the turn. If a card is gained but trashed it does not count.

• We care about only what is theoretically possible, not what is reasonable, so you can dictate:

• What other players choose to do

• Shuffling outcomes or any other source of randomness

But the result must still be possible, meaning that there must be some path through proper play that arrives at the turn and all moves in the turn must be legal.

• You may choose to play with any number of players.

• To keep the scope a little small I would also like to ignore black market.

Just thinking about this on my own I came up with a way to gain 75 cards now 141 cards in a single buy which I posted as an answer to get the ball rolling. I had a lot of fun coming up with it but I'm sure someone who knows the newer sets can come up with something way better.

1: I bought border village, which allowed me to gain cache which gave be two additional coppers (which I ended up turning to silvers with my trader)

• I can’t easily prove it off-hand, but I suspect that the answer is infinite, or bounded only by the total number of cards in the game. Apr 21, 2019 at 14:31
• @GendoIkari It would be nice to see an engine that can pick up arbitrary cards if you can find it. Even then making the engine smaller will improve your gains since you will have more cards to pick up. Apr 21, 2019 at 14:36
• I know for sure that there exist engines to go infinite; even emptying the entire supply on the first turn. It just isn’t all the result of a single buy. Apr 21, 2019 at 14:38
• Apr 21, 2019 at 14:39
• “If a card is gained but trashed it does not count.” Good restriction. This will probably be key to prevent the answer from being infinite. Apr 21, 2019 at 14:47

You can gain over 200 extra cards without using extra buys. The limit to the number of buys will come from component limits rather than anything inherent in the game, the most important number being the number of each treasure card you play with (as there are at baseline only 136 cards to gain). Ignoring that, the number of types of kingdom cards and the number of each kingdom card in play is also a substantial limitation as you can only pick a subset of the following abilities to use together in an actual game.

# Mechanisms of gaining extra cards

There are four distinct ways to gain extra cards during the buy phase.

1. Extra buys. This is the normal way, and so is not what we're considering here. Via action chaining and action replication, the limit on extra buys you can get comes purely from component limits.

2. Action hacks. The Innovation project lets you play an action card during your buy phase, and there are a bunch of actions that let you gain cards.

3. Triggered abilities that cause you to gain cards.

4. Free cards. Treasure Chest gives you an extra card every buy phase.

All of this assumes arbitrary setup and that you are going to buy a King's Court for maximum action hacking.

# Action Hacks (260 extra cards*)

Have the following in your hand:

Now when you buy a King's Court, you use that to play an extensive tree of King's Courts and Throne Rooms, which will letting you then play a bunch of other action cards that will happen many times. I believe the optimal way to play it is Throne Rooms first and King's Courts second, giving you ability to play 18 actions 3x each and 11 actions 2x each.

If we rig the game (let's say everyone is playing big money with massive decks) and it's 6 player, Thief will gain you five cards every time, so that's one of the one we want to use on the 3x actions. Beggar gives the second most (3 cards per shot), so this is what we want to use the rest of the 3x actions on. This is already 216 cards*. We can then use the remaining 2x actions on Develop/Remake (2 cards per shot) for another 44 cards.

* This number may be lower in practice depending on how many coppers (and silver if you use Trader) are in the supply.

# Triggered Abilities (100+ extra cards)

The cards in this category I know of that work with the action hack above are:

(Hoard and Port aren't going to work because they only trigger off of buying a certain type of card.)

Taking component limits into account, we're only going to be able to use 10 of each of the triggered ability cards. The cards listed above let you gain over 100 extra cards (given we have some way to trash cards during the buy phase).

# Maximum without projects (50 extra cards)

Without using the Innovation project, the limit here is going to be the most triggers we can chain off of one buy.

In this case, I believe the optimal move is to play 10x Hagglers, 10x Hoards, and then buy a Province. This will let you get 20 extra cards, 10 of which can be Border Villages, which can in turn let you get 10 Caches or Death Cards, which will give you 20 more cards. This gives you a total of 50 extra cards.

# With innovation I was able to get 356 (only bounded by number of cards)

4p game (opponents aren't buying anything)

Using the following cards:

12 Colonies
12 Providences
12 Duchies
12 Estates (Est for short)

10 Platinum
30 Gold
40 Silver
32 Copper (C for short)

30 Curses
30 Ruins

9 King's Court (KC for short)
8 Overlord
9 Watchtower
10 Lurkers
10 Feasts
10 Pillage
8 Inventors
10 Death carts
10 Young witches
10 Tournaments
10 Druids (swamps gift is one of the choices)

15 Spoils
12 Will-o-wisps
5 Prizes

Innovation (you have a cube on it)
Pathfinding (+card on overlord)

2 platinums
7 c
3 est
1 kc
2 inventors
2 overlords
1 watchtower

2 platinums
1 kc
1 inventor
1 overlords

Next cards are:
Watchtower
Overlord
Inventor

1. Play platinum. Buy kc. Play it with innovation.
2. Play kc
3. Play inventor 3x (gain some cards)
4. Play overlord as feast (gain a card) then lurker (gaining itself and topdecking using watchtower) then kc. (+3 cards from pf)
5. Play inventor 3x (now all cards are 5 or less) 6 . Repeat step 4 until all cards in supply are gained.
6. Before all pillages are gained do step 4 but play overlord as pillage rather than feast. (Do this 8x to gain all spoils)
7. All cards will be in your hand since you are drawing 3 cards for every one card you gain.
8. Use your kc and overlords to play druids and tournaments to gain prizes and will o wisps.
• What do "kc" and "cool" stand for? Could you expand on the card names in full at least the first time you mention them, for those of us less familiar with the cards? May 20, 2019 at 9:30
• @doppelgreener Based on context, KC = King's Court, Cool = Colony May 20, 2019 at 13:14
• This doesn't work. Innovation does not let you use extra actions gained during your buy phase (which is a key assumption of this answer)
– Zags
May 20, 2019 at 17:30