Ill-Gotten Gains is a good illustration of how bad a card has to be in order to be an on-gain Curser. $5 for a Silver that gains you a Copper is an absolutely miserable deal, and yet the Curse-on-gain is so powerful that IGG is still one of the strongest cards in the game. It is first (and currently only) card which can put a Curse into your opponent’s deck before their first reshuffle. The longer the Curse is in a deck, the more disruption it will cause, and the more damage it will do.
Similarly, the curse is “unblockable” by conventional means. Everybody knows that cursing is the strongest type of attack in Dominion, but IGG is not an Attack card and the distribution of Curses is not triggered by playing the card. Because of this, Moat and Lighthouse can do nothing to block the Curse, and you can’t even reveal a Horse Traders or Secret Chamber to “make up” a little bit for taking a Curse. Trader and Watchtower, however, can still be used to mitigate the effects of the IGG as they react to (would) gaining the Curse, rather than an Attack being played.
The real reason IGG is such a power card, however, is what happens after the IGGs are gone: now there are not one but TWO empty piles: IGGs and Curses. The game will now end not when Provinces are depleted, but when ANY single pile is depleted.
At this point, your deck is ideally full of Coppers and IGG’s. Your opponent is stacked full of Curses. And as we know, in a Duchy rush, Coppers are important. What better card for a Duchy rush than a card that simultaneously lets you end the game after exhausting Duchies while fueling your deck with the treasures it needs to buy the Duchies? Of course, if you draw Copper/Copper/IGG/IGG/IGG and feel you need the points, grab the Province. But if you’re ahead after the IGG race, you can usually end it pretty easily just by buying Duchies and gaining Copper at every opportunity.
If you like to do something ‘fun’ and not-necessarily optimal every now and then, there are a LOT of interesting things you can do with IGG other than rushing three piles with Duchy. Just check out the Game Reports subforum on Dominion Strategy and you will see plenty of examples of people using trash-for-benefit with IGG (who cares about losing a sub-Silver when you get $5 worth of benefit for it!), or even using IGG to facilitate a Coppersmith and/or Counting House strategy which are usually too weak to play at a competitive level.
IGG isn’t always the dominant strategy though. There are cards which can cause enough disruption to the IGG Duchy rush that make it a losing proposition. Essentially, any card which can cause the IGG and Curse piles to deplete at different rates will upset the rush. If the Curses run out first, you’ve got to spend $5 turns buying cards worth less than Silver and not even hurting your opponent in the process before you can start on the Duchies. If the IGGs run out first, well, you’re in trouble.
Other strong cursers are the first of these card that come to mind (they empty Curses quicker than IGGs). So when Witch and Mountebank are out, you should invest in them first before switching over to IGG. Less common, but equally impactful on IGG are cards that affect the Curse/IGG balance: Ambassador, Watchtower, Trader, Embargo. And as always, Masquerade and Jack of All Trades throw a wrench into any cursing strategy. Jack in particular refocuses the IGG game onto Provinces rather than a Duchy rush.
- 5/2 split to give your opponent a curse before they shuffle the first time.
- Coppersmith/Counting House and other Copper-based strategies.
- Can provide support for other Cursers.
- Other fast cursers conflict with an IGG/Duchy rush.
- Opponent’s heavy trashing MIGHT be able to overcome an IGG rush, but then you should trash away your Copper too and carry on as of the IGG rush didn’t happen.
- City. They’ll be powered up for both players, but if you’re focusing your $5 buys on IGG your opponent will have more Cities.
- Masquerade/Jack of All Trades