Non-Attack interaction
Interaction between players in Dominion comes about through different mechanics. The primary ones are Attack cards and the Supply -- the cards there are accessible to all players enabling players to deny others access to cards by emptying a pile, and to exert influence over the end of the game which affects both players. The effect of denial can be more pronounced if fewer copies of certain cards are available - especially for split piles like Knights and Encampment - and also extends to non-supply cards like Travellers and Prizes. Finally, this effect also appears with respect to the Black Market deck as well as Boons and Hexes.
Other than these core mechanics, there are other effects that cause interaction between players, including some that affect all players equally (like Family of Inventors), some that give minor benefits to other players (like Council Room), some that concern resources that can be fought over (like Artifacts and many Landmarks), and Reactions which can often be used in reaction to another player's doings.
The distinction between Attack-based and non-Attack interaction is somewhat fluid: On the one hand, there are effects that closely resemble attacks but are not (like Haunted Castle), on the other hand, some Attack cards also have interactive effects beside their primary Attack effect, for example Soothsayer (giving a minor bonus to another player), Rogue (interacting with the trash that is accessible to both players), and Black Cat which reacts to another player gaining a card to attack them.
Non-Attack interactive cards
Cards in italics have been removed.
Cards that depend on the state of the supply
Some cards have extra effects depending on the state of the supply which are sometimes highly important (such as with City).
Command variants that play cards from the supply (like Band of Misfits) also depend on the supply because they can't play cards from empty piles.
- Salt the Earth can influence the supply without a player gaining a card.
Cards that give a small benefit to other players
Cards whose effects depend on another player's deck, turn, or hand
- Tribute
- Monkey
- Smugglers
- Pirate
- Possession
- Tournament
- Fool's Gold
- Treasure Hunter
- Chariot Race
- Gladiator
- Sheepdog
- Goatherd
- Falconer
Cards that allow another player to make a decision
- Gathering cards:
- The trash:
Cards that change who controls a unique resource
Other interactive effects
- Masquerade swaps cards about between all players' hands.
- Embargo tokens affect all players equally once placed.
- Mountain Pass prompts a bidding event among all players after the first Province has been gained.
- Tax puts Debt tokens on a supply pile that affect whichever player is next to buy from that pile.
- Invest gives one player a bonus when another player gains a copy of a certain card
- Family of Inventors makes a non-Victory Supply pile cheaper for all players
- Trade Route
Fringe cases
- The Reaction cards Moat, Secret Chamber, Diplomat, Horse Traders, Beggar, Caravan Guard are interactive, but only in the presence of Attacks.
- Other Reaction cards (Watchtower, Tunnel, Trader, Market Square, Faithful Hound, Sheepdog, and Village Green), as well as many other cards, have effects that can be triggered on other players' turns by some Attacks or other interactive cards.
- Ill-Gotten Gains, Raid, Haunted Castle, and Circle of Witches are interactive and aren't technically Attacks, but they fill the same function as Attacks do.
Trivia
Dominion is occasionally caricatured as "multi-player solitaire", in that in some circumstances it is possible for each player to independently build their own deck, with no direct interaction between different players' strategies and deck compositions. This tendency is mitigated, however, by the presence of cards that affect players other than their owners; this arguably makes the game more fun and strategic by keeping each player involved even during other players' turns. Attack cards are interactive in this way, but also tend to delay the game and are unpopular with some players; for this reason Donald X. Vaccarino thought it important to include non-Attack cards that cause interaction between players as well. At an early stage of development non-Attack interaction was the theme of the "War" expansion that eventually was revised into Dark Ages; it ended up being a subtheme of Prosperity, an expansion with relatively few Attack cards. But some such cards are present in each expansion.
