Transmogrifier

Transmogrifier is a shared event (appearing in Acts 1-3) where a machine transforms one card of your choice into a random card of the same rarity. You select one card from your deck to transform, and it is replaced with a randomly chosen card of the same rarity tier (Common into Common, Uncommon into Uncommon, Rare into Rare). The transformation is permanent and costs no gold or HP.

Transmogrifier is valuable primarily when you have a weak card of high rarity that you want to replace. Transforming a poor Rare card gives you a random Rare, potentially landing a much better card. Transforming a Common card gives you a random Common, which may or may not be an improvement. Using Transmogrifier on Curses is not possible — they cannot be transformed. The event is best used to upgrade lateral moves within a rarity tier, particularly for removing dead cards that were added from other events.