Frail

Frail is a debuff that reduces the Block gained from all cards by 25%. It lasts for a number of turns equal to its stack count and decreases by 1 at the start of each turn. Frail stacks extend the duration additively when multiple applications are received.

Frail is less commonly applied compared to Weak or Vulnerable, but it is a significant threat when paired with high incoming damage. The Collector boss can apply Frail along with Weak and Vulnerable simultaneously, which can severely compromise your defensive options. Some cards like Doubt (a curse) permanently apply 1 Frail per turn. Building sufficient Block output to compensate for Frail, or having alternative defensive tools, is important in these encounters.