Necrobinder The Osty Deck Build — Slay the Spire 2 Guide

Grow Osty into an unkillable front line — Summon synergies stack health that never wears off.

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.

Related

• Necrobinder build hub — all archetypes overview
• Builds Overview
• Necrobinder card table
• Card Tier List