What is Reaper?
Area attack that can restore HP based on damage actually dealt, particularly with Strength.
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
Save for multi-enemy fights or moments after Strength scales.
What to avoid
Using it into low-health targets without setup can waste the healing opportunity.