Corrupt Heart

The Corrupt Heart is the final boss of Slay the Spire, fought in Act 4 with 750/800 HP. It has a passive called Beat of Death that deals 1 damage for every card the player plays, punishing card-heavy decks. It uses Debilitate (applies 2 Weak, 2 Frail, 2 Vulnerable), Blood Shots (multi-hit damage), and Echo (damage that also buffs itself). At the start of combat it has Invincible, which caps the maximum damage it can receive in a single turn at 300.

The Corrupt Heart is a multidimensional challenge: Beat of Death punishes playing too many cards per turn; Debilitate compromises both offense and defense; and the 300 damage cap prevents one-shot victories. The ideal strategy balances efficient, impactful card plays with strong Block to survive its attacks. Builds with strong single-hit damage rather than wide card draw tend to perform best. Reaching the Corrupt Heart requires collecting all three Keys in Acts 1-3, making it an optional but ultimate test of mastery.