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Necro Mastery — Necrobinder Power Card in Slay the Spire 2

Updated 17 Oct 2026 Source Slay the Spire 2 card data (spire-codex.com API), 577 cards retrieved 17 October 2026 By
Data status: The facts on this page were checked against the source named above. Game values can still shift with a patch, so re-check anything that looks off.
Necro Mastery card art
Necro Mastery

Summon 5. Whenever Osty loses HP, ALL enemies lose that much HP as well.

CharacterNecrobinder
TypePower
RarityRare
Cost2 Energy
TargetSelf

Card text

Summon 5. Whenever Osty loses HP, ALL enemies lose that much HP as well.

Upgraded: Summon 8. Whenever Osty loses HP, ALL enemies lose that much HP as well.

Other Necrobinder cards at 2 Energy

  • Deathbringer — Apply 21 Doom and 1 Weak to ALL enemies.
  • Delay — Gain 11 Block. Next turn, gain 1 Energy.
  • Eidolon — Exhaust your Hand. If 9 cards were Exhausted this way, gain 1 Intangible.
  • Flatten — Osty deals 12 damage. This card costs 0 1 Energy if Osty has attacked this turn.
  • Forbidden Grimoire — At the end of combat, you may remove a card from your Deck.
  • High Five — Osty deals 11 damage and applies 2 Vulnerable to ALL enemies.

Where to go next

All 577 cards — the full table, filterable by character. Efficiency tier list — every measurable card ranked.

Rarity system explains how often this card appears. Enchantments covers the modifiers that can change it.

Frequently asked questions

What does Necro Mastery do in Slay the Spire 2?

Summon 5. Whenever Osty loses HP, ALL enemies lose that much HP as well.

What does upgrading Necro Mastery change?

Summon 8. Whenever Osty loses HP, ALL enemies lose that much HP as well.

How much does Necro Mastery cost?

2 Energy. It is a Rare Power card.

More Slay the Spire 2 guides

Sources

Figures and item data on this site are read from the game’s own reference wiki before publishing. Where a value could not be confirmed there, the page says so instead of filling the gap.