Necrobinder in Co-op: Osty and Doom Done Right

How Osty and Doom Actually Work

• 1
  Osty intercepts unblocked attack damage aimed at you.

  Overflow after Osty dies hits you. Osty does not eat Burns, Infection, Toxic, or most HP-loss effects.

• 2
  Osty attacks ignore your Strength and Weak.

  Summon adds HP to Osty, or revives it at 1 if dead. The starting relic summons 1 at the start of your turn.

• 3
  Doom executes when stacks reach current HP.

  It resolves at the end of the enemy's turn, so they still act once. Anyone's damage - Poison ticks, orbs, Ironclad slams - can push HP into that window.

• 4
  Other players can get their own Osty

  if they pick up Summon effects in multiplayer.

1How to Play the Fight

• 1
  Turns 1-2: feed Osty before you greed.

  Play every cheap Summon. Bound Phylactery already gives +1. Bodyguard, Invoke, Spur, Dirge, and Reanimate are the keep-the-hand-on-the-field package. If Osty dies turn 1 of a hallway, you are the lowest-HP character with no shield.

• 2
  Call the tank plan in chat.

  Tell the group Osty is up so attacks hit you first. In co-op, Osty only soaks your incoming attacks unless a teammate also has one.

• 3
  Put a Doom number on the highest-HP threat, then stop overlapping damage.

  Say the number out loud. Teammates chip to that number - they do not dump a 40-damage finisher that wastes the execute.

• 4
  Use Doom as a team finish, not your only offense.

  Countdown plus Death's Door or Sleight of Flesh still gives Block or on-apply damage even without a pure execute deck. Poison from Silent is the cleanest partner - it ticks between turns into the threshold.

• 5
  Souls are the consistency layer for co-op.

  Generate and cycle Souls; if you have the card that gives Souls to everyone, play it. Haunt-style "damage when a Soul is played" has been reported to interact across players - test it in your patch.

• 6
  Only sacrifice Osty on purpose.

  Bone Shards, Sacrifice, and kamikaze lines deal off Osty's HP - that removes the team's extra health bar. Have Bodyguard or another Summon in hand before you pop it.

• 7
  Boss plan:

  Osty soaks the first big hits while the table applies Weak, Vuln, and Poison. Keep stacking Doom on the boss; the aggressive partner pushes remaining HP into the line. Do not spend the setup turn attacking with your own Strikes if that lets Osty die.

Key Decisions

Common Mistakes to Avoid

• ✗
  Treating Osty as a pet you buff when convenient. It is your HP bar.
• ✗
  Stacking Doom then watching a teammate overkill the same target.
• ✗
  Assuming Doom kills before the enemy acts. Plan for one more hit.
• ✗
  Thinking Strength-down or Fragile weakens Osty. It does not - energy-for-Strength cards are often free in Osty decks.
• ✗
  Dirge-core Osty engines after the Exhaust nerf: still good with energy, not an auto-win by itself.
• ✗
  Letting non-attack damage hit you while a fat Osty stands there. Status and HP loss bypass it.

Reference Images

Osty as a giant hand next to Necrobinder - the visual players keep posting

Self-Doom plus big Osty - the screenshot players used when the engine clicked