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Necrobinder mechanic · Main v0.107.1 · Beta v0.111.0

Osty & Summon

A second health bar that can be saved, spent and rebuilt.

Summon heals and raises living Osty's combat Max HP, or revives him at the Summon amount when dead. Osty absorbs unblocked Attack damage before Necrobinder and can convert his current or Max HP into attacks and defense.

Read the exact rules
Necrobinder and Osty on the official character selection screen
Official character-select screenshot showing Necrobinder with Osty. Source: Mega Crit press kit

Rules before recommendations

How Osty & Summon works

Summon while aliveRaise current and combat Max HP by X
Summon while deadRevive Osty at X HP
Damage coveredUnblocked Attack damage
Unleash readsCurrent HP
Sacrifice readsCombat Max HP

After Block, Attack damage hits Osty first. Any amount beyond his current HP reaches Necrobinder. Burn, Toxic and most direct HP loss bypass him because they are not Attack damage.

Living Osty gains both current and combat Max HP from Summon. Dead Osty revives with the Summon amount instead. Bound Phylactery supplies Summon 1 at each turn start.

Unleash scales from current HP. Protector and Sacrifice care about Max HP. A damaged Osty can therefore produce a weak Unleash and a strong Sacrifice in the same hand.

Osty attacks ignore the player's Strength and Weak. If Osty is dead when one resolves, the attack has no effect.

The resource loop

What you are trying to convert

  1. 1

    Summon to grow Osty's current and combat Max HP.

  2. 2

    Let Block and Weak preserve that stored value while Osty catches unavoidable Attack damage.

  3. 3

    Use current HP for Unleash or accumulated Max HP for Protector and Sacrifice.

  4. 4

    Play normal Osty attacks before killing him, then Summon to begin the next cycle.

The pieces that matter

Cards and relics that support Osty & Summon

Cards

BodyguardThe starting and most dependable Summon card.

UnleashTurns Osty's current HP into bonus attack damage.

ProtectorUses Osty's combat Max HP instead of current HP.

Sic 'EmMakes following Osty hits rebuild HP through Summon.

RattleRewards playing other Osty attacks first.

SacrificeKills Osty to convert Max HP into a major Block turn.

ReanimateProvides a large rebuilding action.

Relics

Bound PhylacteryGuarantees Summon 1 at each turn start.

Phylactery UnboundProvides a larger starting and recurring Summon engine.

Bone FluteMakes every Osty attack produce Block.

Execution

Play tips that save real HP

  • Think of Summon as a deposit, not temporary Block. It protects later turns and may become damage.
  • Use Unleash before Osty absorbs a large hit when the current-HP bonus matters.
  • Play ordinary Osty attacks before Bone Shards or Sacrifice, then rebuild him after the spend.
  • Use Sic 'Em before the rest of the Osty attack chain so each hit can return value as Summon.
  • Draft ordinary Block and Weak for Burn, Toxic, direct HP loss and attacks that would otherwise empty Osty too quickly.

Common mistakes

  • Treating Summon as ordinary Block and ignoring that it carries value between turns.
  • Expecting Strength to increase Osty attack damage.
  • Playing Osty attacks while Osty is dead.
  • Using Sacrifice before the attacks that still needed a living Osty.

Experimental branch

Beta v0.111.0 differences

Summon rulesNo direct base-rule change found

The same current-HP, Max-HP and revive logic applies.

SacrificeBlock rises from twice to three times Osty's Max HP

Beta can cash a developed Osty into a much larger defensive turn.

Continue with Necrobinder

See where this mechanic fits beside the character's other build packages, Act 1 picks and relic priorities.

Open the Necrobinder guide