Guildhall can enable some very fast, consistent “big money” decks that drain Provinces before other, more elaborate strategies have time to get enough points to win. Most treasure gainers have strong synergy with Guildhall, but three of them are powerful enough to be called combos.
Each of these decks is somewhat vulnerable to attacks, just like any other “money density” deck might be — if you’re being hit with a junking or discard attack, you can expect to be slowed down by a few turns, so consider investing in those attacks to fight a player who wants to go for these.
Guildhall/Masterpiece can buy its fifth Province around turn 11, and its eighth Province around turn 15. The combo is very consistent in getting to these points in time, mostly because it uses Coffers as its main form of economy rather than relying on getting a good hand to hit Province.
You’ll want to open in a way that maximizes your chances of hitting $5 on turn 3 or 4 — Silver/Silver is pretty good for this, but you can often find some kingdom support to help you out here. Get a Guildhall on your first $5 hand and at that point, get a Masterpiece on every $4+ hand, spending all of your Coffers each time. Do this until you have at least two $7+ Masterpieces, and consider getting a third Masterpiece like this if you think you’ll need more than 5 Provinces to win the game. If you have $3 or less, just get a Treasure card.
After this point, just use your Coffers to buy a Province every turn, usually starting around turn 7 or 8. If you don’t have enough coffers to get a Province, just get another Masterpiece to stock back up.
Guildhall/Beggar does not have the same consistency as the other two combos in this article. Because of the risk of colliding Beggars, you can get a bad draw, slowing you down a few turns. Without any collisions, you can expect to have your fifth Province around turn 12 and your eighth Province around turn 16.
You’ll want to open Beggar/Beggar and get a Guildhall on your first $5 hand. After that, you’ll immediately want to either spend your Coffers to buy a Province, or get another Beggar (or just a Treasure card if you don’t think you’ll play the Beggar before the game is over).
Similar to the Masterpiece combo, you’ll want to open in a way that maximizes your chances of hitting $5 on Turn 3 or 4. Frequently you’ll get two Silvers on your $4 hand and something else to help out on $3. Get a Guildhall on your first $5 hand.
After you have Guildhall, you’ll want to spend your turns up through turn 7 (the third reshuffle) just getting Delves and stockpiling Coffers — make sure to buy a Copper at the end of your Delves each turn, and if you have an odd amount of money, spend a Coffers to get an extra Delve. If you have $7 of more without spending Coffers, it’s Ok to get up to one Province before this shuffle if you think you’ll need more than 5 Provinces to win.
After this point, get a Province at every opportunity, spending as many Coffers as needed. You’ll usually have your fifth Province around turn 12, and your eighth Province around turn 16.
A video of these “combo” decks can be found here. This article is a summary of that video, but note that there are a few discrepancies — when playtesting for this article, some optimizations were found that improve the play of these combos beyond what the video suggests.