An attack's printed damage is only the starting point. To decide whether a card kills an enemy, account for its Strength scaling, the modifiers on both creatures, rounding, and the enemy's remaining Block.
These examples use Slay the Spire 1. They assume normal attacks, one enemy that survives until the final hit, neutral stance, and no effects beyond those named.
Which attack benefits from Strength?
Heavy Blade costs 2 energy and adds three times your Strength to its 14 base damage. Its upgrade changes the Strength multiplier to five; base damage stays 14. Sword Boomerang costs 1 energy and adds Strength to each of its three 3-damage hits. Its upgrade adds a fourth hit.
With 3 Strength and no other modifiers:
| Card | Calculation | Damage before Block |
|---|---|---|
| Heavy Blade | 14 + (3 × 3) | 23 |
| Heavy Blade+ | 14 + (5 × 3) | 29 |
| Sword Boomerang | (3 + 3) × 3 hits | 18 |
| Sword Boomerang+ | (3 + 3) × 4 hits | 24 |
Heavy Blade+ gains 6 damage from the upgrade in this situation. Sword Boomerang+ also gains 6, at a lower energy cost, but each hit chooses a random living enemy. With several enemies, its total is not guaranteed damage to the target you need to kill. The game recalculates each hit against its target.
Negative Strength follows the same card rules. At −3 Strength, Heavy Blade deals 14 − 9 = 5, while Heavy Blade+ reaches 14 − 15 = −1 and is clamped to 0. An upgrade can therefore reduce this card's damage while your Strength is negative.
Follow the calculation to HP loss
Suppose you have 3 Strength and Weak. The enemy has Vulnerable and 8 Block. For Heavy Blade+, the stages are:
| Stage | Operation | Running damage |
|---|---|---|
| Base damage | Start at 14 | 14 |
| Strength | Add 5 × 3 | 29 |
| Weak | Multiply by 0.75 | 21.75 |
| Vulnerable | Multiply by 1.5 | 32.625 |
| Rounding | Round down | 32 |
| Enemy Block | Subtract 8 | 24 HP lost |
The fractional value survives both multipliers. Rounding 21.75 down before applying Vulnerable would incorrectly produce 31 damage instead of 32. Block is consumed after damage has been calculated; it does not reduce the number that Strength, Weak or Vulnerable modify.
Sword Boomerang+ in the same situation calculates each hit as (3 + 3) × 0.75 × 1.5 = 6.75, rounded down to 6. Four hits deal 24 damage before Block and 16 HP after consuming the enemy's 8 Block. Rounding the combined 6.75 × 4 would incorrectly produce 27 damage.
Against an enemy with 20 HP and 8 Block, Heavy Blade+ kills in this situation; Sword Boomerang+ leaves 4 HP. Its lower energy cost may still leave you another card to play. Damage per energy and the damage needed to kill answer different questions.
The game's operation order
The game processes phases in order. Within a creature's power list, lower priority numbers run first. A priority in one phase does not move a power ahead of another phase.
For a normal card attack calculated against an enemy:
- Start with the card's base damage and any card-specific calculation.
- Apply the player's relic damage modifiers.
- Apply the attacker's power modifiers. Strength uses priority 5; Weak uses 99, so Strength is added before Weak multiplies the result.
- Apply the attacker's stance. Wrath multiplies outgoing normal damage by 2; Divinity multiplies it by 3.
- Apply the target's incoming-damage power modifiers, including Vulnerable.
- Apply the attacker's final-damage power modifiers, then the target's final incoming-damage power modifiers.
- Clamp negative damage to zero and round down to an integer.
- Resolve the hit: the monster's damage handler checks Intangible, consumes Block, then runs the attack and attacked callbacks before subtracting HP.
This is an order of game operations, not a rule that every addition in the game happens before every multiplication. Card overrides and later hit callbacks matter. The worked examples omit those extra effects so every number is accounted for.
Heavy Blade's code temporarily multiplies the Strength amount before calling the shared calculation, then divides it back afterward. That division restores the power's stored amount; it does not divide the resulting damage.
Weak and Vulnerable stacks are duration
Two stacks of Weak do not mean half damage. Normal Weak multiplies attack damage by 0.75 regardless of its duration. Normal Vulnerable multiplies incoming attack damage by 1.5.
Relics can change those factors: Paper Krane makes Weak on enemies use 0.6; Paper Phrog makes Vulnerable on enemies use 1.75; Odd Mushroom makes Vulnerable on the player use 1.25. These conditions distinguish the attacker from the target. They cannot be represented by a single generic effect amount.
A Skill example: Dexterity before Frail
An unupgraded Ironclad Defend starts at 5 Block. With 2 Dexterity and Frail, it grants:
(5 + 2) × 0.75 = 5.25 → 5 Block.
Dexterity uses priority 5 and Frail uses 10, so the addition comes first. After the ordinary Block modifiers, the game runs its final Block modifiers, clamps a negative result to zero, and rounds down. Applying Frail to 5 and only then adding Dexterity would incorrectly produce 5.75 instead of 5.25.
Defend+ starts at 8 Block, so the same conditions give (8 + 2) × 0.75 = 7.5 → 7 Block. The upgrade gains 2 usable Block here, despite adding 3 to the base value.
These card calculations do not establish a universal formula for every source of Block, HP loss, orb damage, or for Slay the Spire 2.