Glass Knife

Glass Knife is a rare Silent attack that deals 8 damage twice for 1 Energy, but each time it deals damage, its damage permanently decreases by 2 for that combat. On the first use it hits for 8+8=16; on the second it hits for 6+6=12; by the third use it's down to 4+4=8. It front-loads enormous burst damage but degrades rapidly with repeated use.

Glass Knife is best evaluated as a high-burst finisher rather than a sustained damage source. Playing it once against a boss can shave significant health, but the degradation makes it less impactful in long fights. It pairs naturally with cards or relics that reset or avoid the degradation — or simply with very fast strategies where the fight ends before multiple uses. Upgraded, it removes the degradation penalty entirely and becomes a consistent 12+12=24 damage for 1 Energy, which is among the highest single-card damage in the game and makes upgrading it transformative.