Throne Room variant
A Throne Room variant is any card that causes multiple plays of other cards: either playing one card multiple times, or playing multiple different cards once each. Normally, playing an Action card costs an Action, but being played by a Throne Room variant has no such requirement. The multiplying power of these cards makes them very useful in engines, and some of them can even be a substitute for villages. Throne Room variants can be used on Duration cards, but if they are required for tracking purposes (such as if they multiply the Duration card's effect), they must be left out until your next turn as well, which can sometimes cause them to miss your reshuffle. However, a higher level Throne Room variant multiplying the one multiplying the Duration does not have to be left out.
One of the distinguishing features of Throne Room variants is that they can create different outcomes than if you had just played the relevant other cards the relevant number of times; e.g. playing two Villages will leave you with 3 Actions, but playing two Villages with Golem will leave you with 4 Actions.
Throne Room variants that play Actions are sometimes called pseudo-villages. Throne Room variants often have a name referencing royalty.
 List of Throne Room variants
- Throne Room - archetype, doubles an Action
- Golem - digs for and plays two Actions
- King's Court - triples an Action
- Procession - doubles an Action, then Upgrades it
- Counterfeit - doubles a Treasure, then trashes it
- Disciple - doubles an Action, then gains a copy of it
- Royal Carriage - can be saved until needed, and more than one can be used on the same card
- Crown - either doubles an Action, or doubles a Treasure, depending on what phase of your turn you're in
- Ghost - digs for an Action and doubles it on your next turn
- Citadel - doubles the first Action you play on each of your turns
- Scepter - replays during the Buy phase an Action that you have in play
- Prince - One-shot that plays a set-aside, inexpensive Action at the start of every turn (does not normally work on Durations or Reserve cards)
The multiplying effect of Throne Room variants is most useful on cards you are less likely to have many copies of, either by being expensive, or having low availability (e.g., being a Prize). King's Court is aptly named here, as its unique ability to triple an effect makes it very useful even on more mundane cards. Using Throne Room variants on other Throne Room variants (Prince and, to an extent, Golem don't work here) can also form the core of an engine, up to even replacing villages, though be careful when using Procession for this, as you may find yourself running out of Processions! For example, King's Court on another King's Court allows you to play three Actions three times. Whereas a single King's Court on a terminal draw card might leave you with a bunch of Actions you can't do anything with, if you played another King's Court first, you now have two more chances to triple cards, and if either of them give at least +1 Action (or is another King's Court), your engine can continue to trundle along afterwards. Once you get to your Buy phase, it's usually better to not do this with Counterfeit; since you can play any number of Treasures, the only benefit to Counterfeiting another Counterfeit is an extra and +Buy, which is usually not worth the cost of trashing the moderately expensive Counterfeit.
Since the effect of playing another Action card does not cost an Action, if a cantrip (or any other card that gives +1 Action) is played, your remaining Actions can actually increase, rather than remaining the same. For example, playing King's Court on a Peddler will leave you with 3 cards drawn, + , and 3 Actions remaining; if you had just played three Peddlers in a row, you would only have 1 Action remaining. This makes engines much more viable in Kingdoms without villages.
Bear in mind that certain effects are not multiplied when their card is. Any card with a "while in play" clause will not have that effect multiplied; for example, Bridge's cost reduction can be multiplied, whereas Highway's cannot. Also, any one-shot with an "if you do" clause referring to its removal from your deck will not be able to be multiplied. Feast does not possess such a clause, and is typically much better in games with Throne Room variants.
The danger of Throne Room variants is that they can be dead cards if they don't line up in the same hand with another Action to play. Thus, adding a Throne Room to a Big Money deck with only a few Action cards is unlikely to actually let you double-play those few Actions very often; they need decks with a relatively high density of Action cards.