Menagerie is one of several Cornucopia cards that is very strong — equivalent to two Laboratories (!) –but probably not worth opening with. Your initial deck of 7 Coppers and 3 Estates is the biggest barrier to Menagerie’s success: early trashing is basically the only way to make Menagerie at all effective before the midgame. Without it, your Menagerie is only going to activate if you have 4 unique cards plus your Menagerie (3 if you have another Menagerie in your hand, since it’ll get counted as unique by the time you play Menagerie), and it’s pretty difficult to get 3 early buys into a hand with a Copper and Estate.
About the only exception to this 4-unique-card requirement are handsize decreasers. Menagerie is a fantastic counter to Militia (assuming you draw it against their Militia, which will happen quite often in multiplayer games), since even in the early game you’d have to be quite unlucky not to draw 2 unique cards with the Menagerie in your (pre-Militia) 5-card hand. You end up with 5 cards after playing the Menagerie, which is the same as if you had not been Militia’d, and more importantly, lets you discard the bad cards to the Militia and hopefully draw better ones.
Voluntarily decreasing your own hand is even better. Warehouse is the easiest approach: with 7 cards, it is usually easy to find 3 uniques, or alternatively simply discard the Menagerie. Outpost is also good, provided you can find some way of drawing your Menagerie in the 3 Outpost cards. Cards that let you discard for some benefit are even better, but with the exception of Hamlet, they (Vault, Horse Traders) tend to require some +Action in order to play the Menagerie. And Haven is a special example: you want to use it to shuffle your repeating cards into the next hand so you can activate your Menagerie, or alternatively shift your Menagerie from hand to hand until you find a good hand for it.
Naturally, Menagerie works well with all those Cornucopia cards that encourage or promote variety. It is a (very) soft counter to Cursing attacks and Swindler, which tend to give you cards you would not have bought.
Finally, otherwise universally good handsize-increasers tend to hurt Menagerie. This is especially true for Durations like Caravan, where the extra card that screws up your Menagerie is probably not worth it.
- Early trashing
- Opponent’s Militia, Goons, handsize-decreasers
- Other discard-for-benefit cards, with some +Action (e.g., Horse Traders, Vault)
- Other Cornucopia cards that reward variety (e.g., Harvest, Fairgrounds)
- Cards that lead to variety (e.g., Black Market, Prizes, opponents’ Cursing attacks)
- Caravan, Wharf, other handsize-increasers
- Total lack of trashing, or other way to get rid of Coppers