Crowns are items that can be placed on a card to have it deploy with the Leader at the start of a battle. Between battles, Crowns may be freely removed and given to different cards; adding or removing Crowns in the middle of a battle will only affect future battles and not the current one.
If a card with a Crown cannot be played for some reason (most commonly encountered with cards that have Recycle), the player is forced to hit the Redraw Bell and discard all the unplayable cards. If a card is created by a card with a Crown (such as by a card with Trash), that created card will not be playable as though it had a Crown. Attempting to play such a card displays a "Play Crowned cards first!" message. Additionally, any created cards will take up space in the player's starting hand, causing them to draw fewer cards; for instance, using the Bom Barrel and adding 4 Junk to the hand means that only 2 new cards will be drawn (as the hand size is 6).
Crowns are mainly purchased from The Woolly Snail. They cost 75 Blings, though only one is sold at each shop. Another Crown may be purchased for another 75 Blings if the player encounters the Woolly Snail again later in the run. If the Blingsnail Bell is active, Crowns cost 80 Blings each, and each time a Crown is purchased the next Crown will cost 10 more Blings. Additionally, a Crown will always be offered after defeating the first boss.
Cursed Crowns are special Crowns that appear while the Tyrant Bell is active, in which case they have a chance to replace regular Crowns whenever they are offered. Cursed Crowns cannot be removed from a card, and reduce the health and attack of the card by 1 each, if such stat changes are possible. Since they cannot be removed, Cursed Crowns are best applied to Items that are generically useful in any fight, rather than fight-specific counterpicks. It's also possible to leverage the attack loss beneficially, as some Items hit allied cards for a benefit (e.g. Peppereaper and Shellbo).
Crowns are exceptionally useful in guaranteeing a card is deployed (or used, if an Item). It also saves a turn that would be needed to play the card. With multiple Crowns, players can even add Crowns to Items to buff other cards before the first turn of the battle. This tactic is helpful in avoiding relying on drawing the cards in the right order and taking turns deploying and using them.
Duplicating a card with a Crown at the Shade Sculptor will display a Crown on the copied card in the animation, but the new card will not have a Crown. Additionally, if the copied card had a Cursed Crown, the copy will still have its stats lowered even though it does not have a Cursed Crown on it.