Action - Reserve
$4
Put this on your Tavern mat.
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When you gain a card costing up to $6, you may call this, to gain a copy of that card.
Discussion:
It's the Smugglers we wish we had. Of course, it costs $4. It's also worth comparing to the other $4 gainers, Armory and Ironworks, or perhaps Talisman is even closer. This seems superior: it can gain cards up to $6, they can be Victory Cards, and you can wait around until you can actually Duplicate the card you want. It doesn't even need to wait around on the Tavern mat like other Reserve cards -- you can call it in the same turn you play it.
The drawback, of course, is that you have to be able to afford the card you're aiming for, so it is susceptible to slogs and attack cards, unlike Smugglers or Jester which can benefit from the opponent's good play. In a Gardens slog, you only need a Workshop in your hand to pick up another Gardens -- the rest of your hand can be junk. A hand of Estate-Estate-Copper-Copper-Duplicate will leave you Duplicating on a future turn. This isn't a bad thing, but like the other gainers, you'll want to be able to call this as much as possible, especially because it can gain $5s and $6s.
Because it can gain cards up to $6, it's much easier to Duplicate Provinces: you only need two highways (or Bridges, etc.) in play, which is feasible even in 3 and 4 player games. Perhaps picking up a few Highways, Duplicating Duplicates and then attempting to pile-drive the Provinces is a viable strategy.
Certainly it works best in engines where you want more of everything. Buy a Border Village for $6, and gain four cards. Get multiple Cultists in your deck even sooner. And in the endgame, pick up extra green cards.
How successful have you been at Duplicating? Do you leave it on the mat until you can gain that key card, or do you use it to gain $4s? Is this an early buy, or one to save for the mid-game?
Earlier discussion:
http://forum.dominionstrategy.com/index.php?topic=12865.0