Dominion Prince Promo

– Prince has you play the same cheap Action every turn for the rest of the game.
– The turn you play Prince, you may set aside a non-Duration non-Command Action card from your hand costing $4 or less; then every turn after that you play the Action at the start of the turn. Command is a type that appears on cards like this; it has no meaning beyond stopping these cards from playing each other.
– If you don’t set aside an Action card, you’ll discard the Prince from play during Clean-up. Otherwise, Prince will stay in play for the rest of the game.
– When playing the set-aside card, normally this means that you follow its instructions.
– For example, if you set aside a Village, you will get +1 Card and +2 Actions at the start of each of your turns.
– The Action card stays set aside. If the card tries to move itself (e.g. Mining Village), it stays set aside and it fails to move. If the card has a bonus that is conditional on moving itself (such as Pixie, which gives Boons only if it trashes itself), you won’t get its bonus. But if the bonus is not phrased so as to be conditional on the card moving (such as Tragic Hero, which trashes itself and gains a Treasure), you’ll get its bonus.
– With cost-reduction, you can set aside a card that normally costs more than $4.
– Cards costing P or D can never be set aside with Prince.
– Playing the card each turn doesn’t use up your normal Action play, and is mandatory.
– At the end of the game, both Prince and the set-aside card are returned to your deck before scoring.
– Prince plays its Action on extra turns from Outpost, Possession, etc.
– If you play this with Throne Room, you can set aside 2 cards on this. You will play both of them at the start of each of your turns. Both the Throne Room and the Prince will stay in play for the rest of the game.
– If you play a Necromancer that plays a Throne Room that plays a Prince twice, the Necromancer will stay in play for the rest of the game.

Other clarifications (from wiki):

– You ordinarily don’t get to play the set-aside card on the turn when you set it aside. However, if you play a Prince via an effect triggered by the start of your turn (e.g. with Piazza and set aside a card, you’ll play the set-aside card on the same turn.
– The start of your turn is part of your Action phase. This matters if you use Prince to play Crown.