Character Overview
The Necrobinder starts with Bound Phylactery as her starting relic, which summons Osty at the start of each combat. Osty starts at 1 HP, absorbs all incoming attack damage via "Die for You", and can be buffed with the Summon keyword to gain more HP. If Osty dies, he reassembles on your next turn with 1 HP.
Her unique mechanics include Doom (an execution threshold — when enemy HP ≤ Doom stacks, they die instantly), Souls (0-cost cards that draw 2 cards, generated by other Necrobinder cards), and Summon (adds HP to Osty). These three mechanical pillars form the basis of her three main build archetypes.
The Necrobinder is currently the strongest character in Slay the Spire 2 due to her two S-Tier archetypes and one solid A-Tier option. See our full STS2 tier list for character comparisons.
Build 1: Doom Stacking
Stack Doom on enemies until their current HP drops below the Doom threshold, then they get executed instantly — regardless of how much HP they have remaining. Think of it like Poison on steroids, except it's an instant kill switch rather than damage over time. One of the most satisfying and powerful archetypes in STS2.
Core Cards
- Doom Spike — Primary Doom applicator. Cheap and stackable. Take every copy offered in Act 1.
- Scourge — Heavy Doom application on multi-target fights. Essential for elite encounters.
- Reaper Form (Power) — Inflicts Doom based on attack damage dealt. Expensive but game-changing once active.
- Time's Up — Finisher card. Deals damage equal to the Doom stacks on the target.
- Scythe (Rare) — 13 damage that permanently increases every time you play it. By Act 3, a single swing can deal 100+ damage.
Key Relics
- Undying Sigil — Enemies with Doom ≥ HP deal 50% less damage. Massive survivability boost.
- Book Repair Knife — Heal 3 HP whenever a non-minion enemy dies to Doom. Offsets the low 66 HP pool.
Strategy Notes
- Stack Doom first, then chip enemy HP down to meet the threshold. Don't rely on Doom alone for damage.
- Vulnerable debuff via Fear or Putrefy accelerates the HP reduction phase.
- Debilitate amplifies Vulnerable, making enemies crumble to the execution threshold faster.
- Always upgrade Soul Spark first at campfires — goes from 6 to 9 damage and adds Vulnerable application.
Build 2: Osty Tank
Pump Osty's HP pool high enough that he becomes an indestructible wall absorbing all damage, then use Osty-specific attack cards to deal massive companion-based damage. Since Osty's HP functions like Block that doesn't wear off between turns, this is effectively an infinite defense build — one of the most beginner-friendly yet powerful strategies in STS2.
Core Cards
- Protector — 1 energy for 10 Summon. Your baseline Osty buff and the card that enables the entire strategy.
- Unleash — Osty attacks with damage scaling off his current HP. Your primary damage source.
- Squeeze — Osty deals 25 base damage + 5 per Osty attack card in your deck. Scales with deck composition.
- Flatten — Pairs with Squeeze for burst combos dealing hundreds of damage in a single turn.
- Pull Aggro — 11 points of effective Block value with additional Summon synergy upside.
Key Relics
- Bone Flute — Gain 2 Block whenever Osty attacks. Adds a free defensive layer on top of Osty's tanking.
- Any energy relic — Osty builds are energy-hungry in the early game. Extra energy is always high value.
Strategy Notes
- Priority: keep Osty alive and growing. A dead Osty means the Necrobinder eats direct damage at only 66 HP.
- Squeeze + Flatten combo is currently one of the highest burst damage combos in all of STS2.
- Snap is an excellent cheap Osty attack with Retain — always useful to hold for flexible turns.
- Avoid Quest Cards in this build — you can't afford dead draws when survival depends on cycling Osty cards fast.
Build 3: Soul Cycling
Turn 0-cost Soul cards into a turbo draw engine, then use Haunt to make Souls directly damage enemies. This build thins your deck to 5–10 cards and cycles through your best plays every single turn. Devastatingly fast but fragile if you don't reach critical mass.
Core Cards
- Haunt (Power) — Each Soul card removes HP from enemies, ignoring Block entirely. Two Haunts make every Soul deal double damage.
- Seance / Dirge / Severance — Soul generators. More Souls = more draw = more damage through Haunt.
- Soul Storm — Generates multiple Souls at once for explosive high-damage turns.
- Undeath — Self-replicating Block card. Pairs with Soul draw engine to find defensive plays consistently.
Strategy Notes
- Deck thinning is absolutely critical. Remove every Strike, Defend, and non-Soul card that doesn't contribute to the engine.
- Haunt bypasses Block and damage reduction — it directly removes HP. Extremely strong against tanky enemies and bosses.
- The build is fragile in Act 1. Consider hybrid starts (Osty + Souls) before committing fully after the Act 1 boss.
- Multiple Haunt copies stack — each additional Haunt multiplies Soul damage. Three Haunts with a thin deck wins most fights in 2–3 turns.
Relic Priority
| Priority | Relic | Why It's Good |
|---|---|---|
| Must-Pick | Bone Flute | 2 Block per Osty attack. Free defense in every build, not just Osty Tank. |
| Must-Pick | Undying Sigil | Enemies with Doom ≥ HP deal 50% less damage. Core for Doom builds, still useful in others. |
| Great | Book Repair Knife | Heal 3 HP on Doom kills. Offsets the Necrobinder's dangerously low 66 HP pool. |
| Great | Energy Relics | Necrobinder is energy-hungry across all archetypes. Any extra energy is always high value. |
| Good | Draw Relics | More cards = faster Doom/Soul cycling. Especially strong with lean, thinned decks. |
General Tips
FAQ
How do you unlock the Necrobinder in Slay the Spire 2?
You need to play one full run as the Regent first. The unlock chain is: Ironclad → Silent → Regent → Necrobinder. You don't need to win the run — just complete it (win or lose).
Can you use cards from other STS2 classes with Necrobinder?
Yes, via the Prismatic Shard relic. Ironclad Exhaust cards and Silent discard synergies work exceptionally well with Necrobinder mechanics. Prismatic Shard builds can be extremely powerful but require careful card selection.
Is the Necrobinder good for co-op in STS2?
Excellent. The Necrobinder provides massive damage while teammates handle defense and support. The community-favorite 3-player composition is Necrobinder (damage) + Ironclad (tank/self-sustain) + Defect (support/orbs). She pairs especially well with characters that can protect her 66 HP while she sets up Doom or Osty.
What is the best Necrobinder build for beginners?
Osty Tank is the most beginner-friendly Necrobinder build. It has a straightforward gameplan (buff Osty, attack with Osty), forgiving card choices, and strong survivability since Osty absorbs all incoming damage. Doom Stacking is stronger overall but requires understanding the Doom threshold mechanic.
Should I pick Doom or Osty cards in Act 1?
In Act 1, take whichever strong cards are offered and don't force an archetype. Both Doom and Osty cards are useful early. Commit to one archetype after seeing what your Act 1 rewards, shops, and boss relic offer. The worst thing you can do is plan a build before the run starts.
Related Guides
Sources & Community References
This guide synthesizes strategy discussion from r/slaythespire, the official STS2 Discord #strategy channel, Mobalytics character guides, and high-Ascension community data. Build ratings reflect Patch 0.98.1 consensus. Last updated: March 9, 2026.