Rats! When we saw this card for the first time we all thought: "Wow, that's thematic! Why would I ever buy that?"
Rats, like most Dark Ages cards, require more finesse and thought than we're used to dealing with in Dominion. In most other expansions, the thought goes into which cards to gain at what time. Once they're in your hand, it's a pretty simple decision in what order to play your cards (+Actions, +Cards, everything else), unless you have clashing Terminals. But cards like Fortress, Death Cart, Junk Dealer and Rats all make you think: "Do I really want to play this now?" And that's good, right?
The PointSo what is the point of Rats? Contrary to popular belief, it's not just to be Donald X's favorite card. There are several instances where you really want Rats. So what are they? Well, first we need to establish what Rats does.
Rats replaces cards in your deck with Rats. More generally, Rats replaces cards (typically of a low cost) with $4 Action cards (which you don't want to use too much). The point of Rats is to replace low-cost junk with higher-cost junk. Very quickly, I might add. If you buy one Rats in the first two turns, and use a Rats every time you see it, you should see a hand of five Rats within 10 turns. Obviously, you want to stop before you get to this point.
So Rats trashes junk to give you other junk to feed to a Trash for Benefit card.
"Well, why didn't I just buy the TfB card in the first place?"
Well, depending on the card, you probably should buy that card in the first place. Any TfB card that does not care about cost probably should take precedence. These would be cards like Moneylender, Spice Merchant, Jack of all Trades, and Altar. The first two of these wouldn't even be able to trash Rats anyway, and the only benefit the other two would get would be drawing another card, and as Terminals, that's of questionable value, at least in an engine deck. So Rats conflicts with several TfB cards.
But we have TfB cards that DO care about cost, and here Rats shines.
What Rats is best withThe Big ThreeThe top three that should come to mind are Salvager, Apprentice and Bishop. All three of these convert the cost of a card into some resource - Coins, Cards and VP, respectively. All of these cards are rather bad at getting rid of your starting Coppers and Estates, and are even worse with Shelters, though Bishop would be the best of these three, since it actually gives a resource when trashing a $0 cost card. So why not trash this $4 card instead? That way, instead of +$0, +0 Cards or +$1/+1VP, you'll get +$4/+1 Card, +5 Cards or +$1/+3 VP/+1 Card. That's a lot better.
Remodel-style cardsEven cards like Remodel and Remake benefit. Do you want to trash two Coppers and get nothing, or trash two Rats and get two $5 cards? Rats turn Upgrade into a less limited Lab/University mashup. Since all of these cards are better when used on higher cost cards, they all do better with Rats. Even lowly Develop, oft derided as slow and cumbersome, gets a boost. Rather than getting nothing for those Coppers you trash one at a time, get a Silver and a $5 card right on top of your deck, after drawing a card!
Other synergistic trashersJunk Dealer does well with Rats. Not as well as the Big Three, given that Rats and Junk Dealer fill similar roles. But getting a +1 Card along with the rest of Junk Dealer is a pretty nice addition. Forge might have you thinking to turn two Rats into a Province, which is a cute trick, but if you're ready to green anyway, that $7 might be better spent on a Gold. Also, that whole trick becomes much harder to pull off with Colonies. Perhaps the greatest combo here is with Death Cart - turn all those Coppers and Estates/Shelters into Actions you're absolutely glad to get rid of every time.
ReactionsWe have three Reactions so far that deal with trashing and/or gaining, and all of them work well with Rats. If you have a Watchtower in hand, you can trash the Rats you gain when you play a Rats, and get +1 Card to boot. So you're cleaning up your deck, and depleting a pile. With Market Square in hand, you can lessen the damage of having to trash a non-junk card to a poor Rats play by gaining a Gold. Even if you're trashing junk, gaining the Gold is awesome. Finally we have Trader. Now, why didn't I include it in the Big Three? It's the other trasher that cares about card cost. But the Action for Trader is really more of a facilitator for Big Money, and if that's what you're going for, you shouldn't really be getting Rats in the first place. However, turning a Rats into four Silvers can be a nice supplement to whatever engine you have going on. The Reaction is also nice, replacing your junk with Silver instead of Rats, though this undermines the whole purpose of Rats, at least with regards to the Big Three or Death Cart - again, this would be a supplement.
Non-trashing optionsWhich expansion heavily emphasizes Actions? Alchemy, that's who! And Alchemy has two cards that go well with a card that fills your deck full of junk Actions. First is Vineyard. Turn all those Coppers and Estates into Rats, and now all those Vineyards are worth at least 3 points more! Just don't trash any Vineyards with them. That would just hurt. Second is Scrying Pool. Scrying Pool works best if you can get rid of your Estates and Coppers and go for a money-less deck. Rats can do just that. Once you've Rats'd away all those starting cards, your Scrying Pools should draw your entire deck, except when snagging on Potions.
Another interesting strategy might be to use Rats to clear out your Coppers for use with Venture or Adventurer. The biggest weakness of these two cards is drawing Copper instead of your better Treasures. If those Coppers are Rats instead, they'll be skipped.
Rats as a DefenseIf all your junk is Rats, certain Attacks suddenly become less painful. Fortune Teller and Rabble clear out all those Rats from your next hand. Saboteur and Knights are suddenly both improving your deck and increasing your next hand. But Rats can also be used to mitigate Curses. Even as the only trasher, it's better to have a Rats in your deck than a Curse. Sea Hag is most vulnerable to this, given that you'll know that the next card you draw with Rats will be one you want to trash.
However, do not use Rats to clean up after Looters. Unless you have a Big Three, it would be much better to have a Ruins (which gives a marginal beneficial effect) than a Rats. Ruins do not effect your score, unlike Curses, so don't feel the need to get Rats if they're the only trasher.
Also, what hand would you most want Possessed? A hand of five Rats! Then your Possessor can't do anything without giving himself Rats, and you'll (hopefully) have a better hand for your turn.
If you're going to use Masquerade with Rats, remember to only send a Rats to your opponent if he did not play the Masquerade; otherwise, he's just going to trash it and draw a card.
When not to buy RatsWhat if there are only straight trashers on the board, like Chapel? In that case, you should probably just go with Chapel. Chapelling Rats would draw you some cards, but it would be faster to just Chapel everything away, and spend your $4 on something that will build your economy.
The one TfB card that cares about cost that you DON'T want to use on Rats would be Procession. Sure, you get a $5 cost card, but you also get two Rats, and have to trash two cards in your hand, which, by the time you get both a Rats and a Procession, you may not want to do.
Rats/Ambassador defeats the whole purpose of Rats. Consider Ambassador to be a straight trasher, like Chapel (in a loose sense). If you're going for that, you don't want Rats anyway. If your jig is to buy junk to send to your opponent, Curses are much cheaper and will hurt him much more.
What if there are no other trashers on the board, outside of the options listed above? DON'T BUY RATS. Let me repeat that. DO NOT BUY RATS IF THEY ARE THE ONLY TRASHER (outside of the aforementioned cases).
So I've bought Rats, specifically to trash it. When do I?Buy the Rats within the first two turns, and use a Rats every time it's in your hand with stuff you want to trash. At the first opportunity, buy your TfB card. Every time it's in a hand with a Rats, use it on the Rats. Once you have your TfB card, only use Rats if it's in a hand without that TfB card, and with remaining junk. In the highly unlikely event that you trash your last Rats before all of your junk is gone, don't worry. You're leaps and bounds in the right direction anyway. You should only ever purchase one Rats. All your other Rats come from playing a Rats.
What about those non-trashing cases?Use Rats whenever you have junk to trash. Be smart with the Rats. If you don't have anything you want to trash to them in hand, don't play them. It's highly unlikely that the next card you draw will be one you want to trash (unless you've Spied ahead earlier), so just regard it as junk for that turn and ignore it. Remember: you don't have to play a card in your hand.
P.S. The Rats pile has 20 cards in it. Don't forget that.
Works best with:
Bishop, Salvager, Apprentice
Works well with:
Remodel-style cards
Death Cart
Junk Dealer
Vineyards
Scrying Pool
Watchtower, Market Square, Trader
Adventurer, Venture
versus trashing Attacks
versus Cursing Attacks
versus Possession
Conflicts with:
Boards without trashers
More efficient trashers (Chapel, Steward)
Ambassador
Treasure-specific trashers (Moneylender, Spice Merchant)
versus Looting Attacks
