Combo: Death Cart and Rats
|Death Cart / Rats|
The strategy is simple - buy a single Rats on your first two turns, and then buy 1 or 2 Death Carts. Otherwise, just buy Treasures. Whenever you have Rats but no Death Carts in hand (as well as an Estate, Copper, Shelter or Ruins), play Rats. If you have Death Cart and a Ruins or a Rats in hand, use Death Cart to trash it. If you're buying Silvers and Golds, the likelihood of your remaining three cards producing is quite high. Rats also draws a card on trashing, increasing the likelihood of getting the necessary extra even further.
This strategy does depend rather highly on shuffle luck - if you draw your first Rats just before your second reshuffle, there is a chance your Death Cart will be drawn with it, meaning you will either have to not use Death Cart that turn (unless you also have a Ruins in hand), or you will have to buy another Rats - and even if they are not drawn together, the Death Cart will not have a Rats to trash that shuffle. This combo can also be frustrated if your Death Cart is drawn without any other Actions. Some games you may get 4 Provinces by turn 13, comparable to a DoubleJack strategy, and others you may find yourself wallowing without any Provinces at turn 20.
This strategy can be done similarly with Fortress, as Fortress can be trashed indefinitely, but because Rats replaces cards in your deck with more Rats, Death Cart/Rats has a higher likelihood of collision than Death Cart/Fortress. Ironworks can also work, as it can non-terminally gain copies of itself, but it does not replace cards in one's deck the way Rats does.