What is Block?
Temporary protection against ordinary attack damage, generally cleared between turns.
This reference covers gameplay decisions in the original Slay the Spire. Character-specific options and relic synergy can change how useful an item is, so consider your current deck, health, upcoming enemy and available resources before applying a strategy.
When and how to use it
Apply enough to stop imminent damage and keep scaling resources available.
What to avoid
Excess Block typically disappears unless a modifier preserves it.