Slay the Spire 2 Necrobinder Builds - Doom & Osty Deck Guides

The Necrobinder runs two proven archetypes in Slay the Spire 2: the Doom Deck, which marks enemies for execution, and the Osty Deck, which turns her skeletal hand companion into an unkillable front line. Both are viable from Act 1 — pick Doom if you like delayed burst kills, pick Osty if you want to play a near-unkillable tank.

How the Necrobinder Plays

The Necrobinder is one of the two new characters in Slay the Spire 2, alongside the Regent — a "sassy lich" from the Spire's forgotten history. She is a fragile but tactically dense spellcaster who works as a duo-unit: you manage both her own limited resources and her companion Osty, a massive reanimated skeletal hand that does the dirty work. Her starting relic, Osty's Binding, is what summons Osty in the first place.

Her strengths, per the Mobalytics character guide:

• Can easily manipulate the Draw/Discard pile
• Excellent tank potential with Osty
• Insane card draw via Souls

And her weaknesses:

• Requires high synergy — she punishes unfocused decks
• A slower playstyle that can be tricky to pilot

Those strengths and weaknesses explain both builds below: each one commits to a specific synergy package rather than mixing everything.

Build 1: The Doom Deck (Execute Archetype)

Doom is a unique "death-mark" mechanic: enemies whose HP is at or below their Doom stacks are executed at the end of their own turn. The payoff is noticeably higher number values on your cards; the cost is that you must survive until the clock ticks down, so a reliable Block plan is part of the deck, not an afterthought.

Core Cards

Card	Why it earns a slot
Blight Strike	A fair damage card on its own, with the potential to be a 1-for-16.
Defile	Not a Doom card, but its high damage-to-cost ratio drops enemies low enough for the mark to matter.
Negative Pulse	AoE Doom plus a bit of Block — fits the defense plan naturally.
Scourge	1-for-13 with built-in draw. What's not to like?
Deathbringer	Large AoE Doom plus Weak — a good combo for the game plan.
Delay	Decent Block with an Energy refund; helpful for survival.
Death's Door	An excellent source of Block once you have a good threshold of Doom cards.
End of Days	Solves the "waiting" problem entirely, as long as you can afford the high cost.
No Escape	Can be an incredibly potent source of single-target Doom.
Oblivion	High potential alongside multiple cheap cards like Souls.
Shroud	Converts Doom triggers into Block throughout the fight.
Time's Up	A strong finisher against large-HP enemies such as Elites and Bosses.

The first six are your early pickups (commons and uncommons you take on the way up the Spire). The last six are the high-synergy payoffs — great, but they require real commitment to the archetype.

Relics to Watch

• Book Repair Knife — a very reliable source of healing, which matters in a deck that tanks while Doom ticks down.
• Undying Sigil — greatly helps weaken enemies on their final turn alive.

How to Pilot It

1. Take your early Doom cards and one or two Block tools; don't greedy-pick payoffs before you have the marks to trigger them.
2. Keep a reliable Block plan — delayed damage is the archetype's big drawback, so avoid tanking unnecessary hits.
3. Splash a small Soul package for card draw. This helps you find your key Doom cards faster and more often instead of relying on the mediocre ones.

Build 2: The Osty Deck (Summon Tank Archetype)

The Necrobinder starts with a significantly lower HP pool than other characters. The Osty Deck turns that weakness into the build's engine: by using the Summon mechanic efficiently you bolster Osty, effectively stacking an endless supply of health — and because Osty's health is not Block, it doesn't wear off between turns.

Core Cards

Card	Why it earns a slot
Pull Aggro	Effectively 11 points of Block value, with the upside of Summon synergies.
Snap	A cheap Osty attack that enables other cards, with extra value from its Retain.
High Five	AoE damage plus Vulnerable is always welcome.
Rattle	A key multi-attack source of damage with great combo potential.
Fetch	A zero-cost attack that cycles itself — great alongside Rattle.
Flatten	Free damage once you have enough Osty attacks in the deck.
Necro Mastery	Converts defense into AoE offense — IF you can reliably let Osty grow.
Reanimate	A big burst source of Summon; only recommended with spare Energy.
Sic 'Em	An Osty attack with great Summon capabilities, particularly alongside Rattle.
Spur	Helpful healing once you can consistently keep Osty alive.

As with the Doom list, the first four are early pickups; Fetch through Spur are the high-synergy payoffs that need commitment.

Relic to Watch

• Bone Flute — it may seem small, but every bit of Block can make all the difference in a build that lives and dies by Osty's survival.

How to Pilot It

1. The build above focuses on growing and keeping Osty alive — protect the hand, and it protects you.
2. There is also a more sacrificial variant built around cards like Bone Shards. Both are legitimate; just be careful not to mix and match the wrong cards, because the two plans want different Osty states.

Meta Cross-Check: Current S-Tier Necrobinder Cards

The Mobalytics card tier list (checked September 2026) puts the following Necrobinder cards in S tier: Demesne, Friendship, Neurosurge, Call of the Void, Sleight of Flesh, Putrefy, Danse Macabre, Lethality, Delay, Reanimate, Enfeebling Touch, Defy, and Reaper Form. Two of them — Delay and Reanimate — also appear in the Osty build's high-synergy list above, which is a good sign the deck-building advice and the current meta agree.

If you want the full card-by-card reasoning, see our Slay the Spire 2 Tier List page, which breaks down cards by tier and updates with each patch.

Which Build Should You Pick?

• Pick Doom if you enjoy planning a kill two turns in advance and don't mind a slower, more deliberate pace. Its AoE marks (Deathbringer, Negative Pulse) also handle multi-enemy fights cleanly.
• Pick Osty if you want the safest route through Act 1–2: an oversized hand absorbing hits forever while your cheap attacks (Snap, Fetch, Rattle) pile up damage.
• Commit to one. The Necrobinder's weakness list says it plainly: she requires high synergy. Half-Doom, half-Osty decks get the drawbacks of both plans and the payoffs of neither.

Both archetypes are sensitive to balance patches — when a new version lands, check the patch notes page for what changed before you lock in a run.

Related Pages

• Slay the Spire 2 Tier List — every card, ranked by tier
• Builds Overview — all five characters at a glance
• Patch Notes & Updates — what the latest version changed