F2P

The attached card's mana cost becomes 0. As an Ultra Rare gem, it is one of the strongest gems in the game. Attaching it to a 3–5 cost finisher card allows that powerful effect to be triggered without any mana expenditure. Note that for combo purposes, the card is treated as a 0-cost card, so combo sequencing must be planned accordingly.

Unlocked by playing Free To Play (cost-0) cards a total of 200 times. Actively building around low-cost cards will naturally achieve this milestone.

Best attached to powerful weapon or finisher cards costing 3 or more. Particularly effective on standalone activation cards unaffected by combo constraints. Making a card free also ensures it can always be played every turn.

Tier S — One of the strongest gems in the game. Making high-cost cards free fundamentally changes the run's power level. An Ultra Rare gem that should be considered first in virtually any build.