P1 gets Rogue, Gold, and Masquerade, while the others do nothing. He then proceeds to pass the Gold to P2, trash it with Rogue, and get it back with Rogue. Now P2 is down a card, the one passed to P3. Repeat until P2 has 2 cards.
Then, Masquerade the Gold to P3, and so on. Eventually, P2 and P3 have 2 cards, and P4 has 1 card.
You can't get the other players below 5 cards with this method.
Right, forgot that bit, but you can just trash with something other than Rogue. Pass a Masq around, have the other player use Masq to trash the Gold in their hand, pass Masq back to P1. Either that, or buy out all the King's Courts, then use the Governor trash option.
I solved this a while back in another puzzle. You only need each player to own a Masq (I know the puzzle doesn't allow it, but Bm can supply the Kc and Possession if needed) to get unlimited starting hand size.
P1 Plays Kc->Possession
P2 Has 3 Possessed turns T1: Kc -> Gov -> Masq (gain Possession) -> Possession; T2: Masq (gain Kc) -> Kc -> Possession; T3-T6 Kc -> Possession; P2's actual turn Kc -> Possession
In total P2 will have 19 Possession turns of P3. Of this the first is spent acquiring Possession (one Possession turn) and the rest will be after getting Kc (54 Possession turns), and as always 3 Possession turn from P3's own turn. You will need to do something hinky with Kc/Gov to be able to play Possession after gaining it.
Basically the number of turns one player's deck can take in row scales with at least A[n] = 3 * A[n-1]
There is no upper bound on this trick.
Okay so say I just do a simple 3^n for may estimated number of consecutive turns. If n = 24 the the last deck will have 282,429,536,481 Possession turns to play. You can then spend a very small fraction of these doing something like (each step may require multiple turns): Player 3 plays Torturer until P5 has no cards in hand (everyone else has at least one card); P5 plays Masq (effectively on card moves from the hand of P1 to P4); Gov for cards (if any of P1-P2 are out of cards); Torturer (P6 now again has no cards in hand); Masq. Eventually you can feed P6 all the cards in the game except those that would end the game which are still in piles and Torturer/Masq/Gov. Torture P4 to 0 cards, play Masq (send Torturer). Now just play like 1000 turns (or whatever) of Gov until P6 draws everything.
Doing this without taking Curses is harder, but I think doable (you have an essentially infinite number of turns for setup, so we can do all sorts of tricks with Gov/Torturer altering card count.
P6 thus begins with a 1000 (or whatever) card hand.
With no Bm, this takes up just 5 Kingdom slots:
Kc, Possession, Masq, Gov, Torturer
A few refinements:
Vault is inferior to Storeroom here:
a. Storeroom comes with a +buy
b. Storeroom allows you to use Tunnel for more gains (with an empty deck, discard 11 or 12 Tunnels, gain 11/12 gold, shuffle, draw 11/12 Tunnels, discard them for cash, gain another 11/12 golds). You lose a net of $32 (8 cards from Tunnels being less numerous than exchange cards and 24 form gained golds that aren't in hand at turn start) for your big discard ... but that just means 16 fewer buys from Travelling Fair so you net at least 6 more cards gained (and I think higher as the less Copper you buy, the more cash you can use in hand to generate $ so I think that should mean you really only lose 8 buys for even better net gain)
c. Storeroom can be the Bane. (not really an issue I think)
You should swap an Exchange/Masterpiece for Embargo/Trader. Yes you lose $21 from your total cash to spend, but using Possession you can set up 100 embargo tokens on the Copper without actually permanently trashing the Embargo. This allows you, without using a single buy, to pile both Curses and Silvers. So you get back $105 ($60 from not needing to purchase +buys for curses and $45 total cost of Masterpiece) so you are ahead $83 and still have a $2 to buy at the end if needed.
I'm not totally sure if the numbers work out, but it might be worth losing the other exchanger to get more gains. For instance swapping the other Exchanger to Stonemason loses us $24 from not discarded cash. However, spending overbuying a 0 cost Stonemason by $4 can net us a large haul of cards. Right now you spend $40 on Dcarts to gain 10 Dcarts and 20 Ruins. With $0 Smason, you can spend 30$ (5x[2+4]) to gain 5 Smasons, 10 Dcarts, and 20 ruins. With 4 of the other Smasons you could overpay by $2 to gain 8 Embargoes. On net that means paying $16 for 12 cards. Total Smason allows you to gain 47 cards for $36; with opportunity cost that, I think should be $50 for 47 cards. You are currently paying $40 for 30 cards (Dcarts and Ruins) and then $38 for 17 coppers for a total of $78 for . So I think the savings are worth decreasing the value of the big discard.
So I think a more optimized solution is to:
1. Put the -$2 token/an arbitrarily large number of embargo tokens on Smason.
2. Use Kc/Possession/Masq/Torturer to setup the mother of all starting hands.
3. Play Sroom - discard all the Tunnels (gain 12 gold), draw 12 Tunnels, discard everything but Trader (gain 12 gold)
4. Overbuy five Smasons by $4 each: reveal Trader to gain the Silver pile then don't reveal Trader to gain the Curses, gain 10 Dcarts & 20 Ruins.
5. Overbuy 4 Smasons by $2 each: gain 8 Embargoes
6. Overbuy 1 Smason by $3: gain last Masq and last Sroom
7. Buy an optimized amount of Ruins/Coppers/Estates (as the more left to buy, the less cash you generate with the big discard)
8. If needed, buy higher priced cards.
