The Necrobinder at a Glance: 66 HP, One Giant Hand, a Kill Condition Nobody Else Has
Start a Necrobinder run and the character sheet hands you the lowest health pool in the game: 66 HP, against 80 for the Ironclad, 75 for the Defect, 72 for the Regent and 70 for the Silent. You unlock this lich by starting a run as the Regent, which is the game politely saying you should already know how the Spire works before piloting a hero with no HP cushion. What you get for those missing hit points is a kill condition nobody else in the roster can copy. Doom is a stacking debuff, and at the end of every turn, any enemy whose Doom count has reached its maximum HP is executed on the spot. Not damaged. Executed. A boss at 240 HP and a rat at 40 HP both die the same way: push the Doom counter up to the max HP number, survive until end of turn, collect the loot.
That rule is why the site build database rates the Doom Execute build S tier and calls the Necrobinder the only S plus answer to co-op HP scaling. In multiplayer, enemy HP is base HP multiplied by player count and an act coefficient, roughly x1.1 in Act 1, x1.2 in Acts 2 and 3, and x1.3 for the Act 3 boss, while enemy attack damage stays flat. A 240 HP boss becomes a four digit damage check for a normal deck. For a Doom deck the fight is identical to solo, because the threshold is a percentage of whatever the max HP happens to be this run. Four players, one lobby, and your Scourge still reads 13 Doom.
Your bodyguard is the other half of the kit. Osty is a giant skeletal hand that fights beside you, attacks when your cards tell it to, and body-blocks incoming hits, for you solo or for the whole team in co-op, where the community assigns this character the board control role. The Summon keyword adds or restores Osty HP, and your starter relic Bound Phylactery summons 1 at the start of every turn, meaning Osty grows a little on its own every single turn of every fight.
Two practical notes before the details. First, this guide reflects the v0.111 beta balance pass, Early Access, and patch v0.108 changed end of turn resolution order so that Doom no longer kills first; if you learned the old timing, relearn it, because end of turn sequencing decides close threshold fights. Second, the mental model that kills new Necrobinder players is importing Poison logic, where every stack is damage every turn. Doom stacks are not damage. They are a bar filling toward one guaranteed lethal moment, and every drafting decision in this guide is about reaching that moment before your 66 HP runs out.
Osty Mechanics: Free Attacks, Body-Blocks and Why Osty HP Is Your Damage Stat
Read Unleash carefully, because it explains the whole character in one line: Osty deals 6 damage plus damage equal to its current HP. Your summon's health pool is your attack scaling. An Osty sitting at 40 HP turns this 1 cost basic attack into a 46 damage swing. An Osty scraped down to 3 HP makes it a 9 damage waste of a card. Every point of Osty HP is simultaneously defense, since it body-blocks, and offense, since Unleash reads the number out loud. That is why Bodyguard, a 1 cost basic skill that summons 5, or 7 upgraded, is not filler. It is your damage steroid and your tank top-up in one play.
The Summon keyword is what grows the hand: it adds or restores Osty HP. Bound Phylactery triggers it automatically for 1 every turn, and Bodyguard does 5 at a time, 7 upgraded. The practical opening against anything that hits hard is Bodyguard on turn one, then start cashing Unleash while the relic trickles Osty upward. Against Act 1 trash like Nibbit, whose fixed loop runs a 12 damage ram into a 6 damage swipe into a Hiss for +2 Strength, you can often skip Bodyguard entirely and just swing, because Osty's floor of 6 from Unleash and Poke outpaces that clock.
Poke deserves its own paragraph because free is free: 0 cost, Osty deals 6 damage, 9 upgraded, and the database calls it a free Osty command every Summon deck wants. It fills hands that would otherwise pass with leftover energy, and it is one of the few 0 cost attacks anywhere that scales for free as Osty grows. When you are deciding between a mediocre common and a second Poke, remember this deck wants to play five cards a turn on 3 energy, and Poke is how.
Matchup notes for the hand. The Phantasmal Gardener fight is four gardeners at 26 to 31 HP each with Skittish 6, meaning the first hit each turn grants them Block and punishes multi-hit decks; the counter is single big hits, one gardener at a time, and Unleash is exactly a single big hit. Byrdonis alternates Dive and Peck for steady mid damage, and Osty body-blocking plus a Defy on the Peck turns the fight into a race you win. The one place Osty genuinely struggles is Vantom, whose 9 Slippery stacks make every individual hit deal 1 damage: do not spend that fight pumping Unleash into a wall. Stack Doom instead, which is the next section.
How Doom Executes Actually Work: Thresholds, Turn End and the v0.108 Timing Change
The glossary definition is short: Doom is a stacking debuff, and at turn end, enemies with Doom at or above their max HP are executed. Every strategic consequence flows from that sentence, and most of them are unintuitive if you came from Poison decks on the Silent. Doom does nothing until it does everything. Twenty Doom on a 30 HP enemy is not two thirds of a kill, it is zero percent of a kill. Two hundred forty nine Doom on a 250 HP boss is a tragedy. The execute only fires when the counter reaches the max HP number, and then it fires completely, so precision matters more than volume.
This has three practical consequences. One: overkill is wasted. Every stack past the threshold is a card you burned for nothing, so in long fights you should be reading the enemy HP bar and stopping the moment the execute is mathematically locked. Two: underkill is fatal in the other direction. End your turn one stack short and nothing happens, and the enemy gets a full free turn to hit your 66 HP body. Three: Doom bypasses per-hit defenses. The database tip for Skulking Colony, which caps the damage it takes per hit and hard-counters single big hit decks, says multi-hit and damage over time, Poison and Doom, bypass the cap. The execute is not an attack. It ignores the tools enemies use to survive attacks.
Timing changed in v0.108. The patch notes list an end of turn resolution order change: Doom no longer kills first. In practice this matters on threshold turns where multiple end of turn effects are pending, so if you have been playing since spring, verify sequencing in the fight log rather than trusting muscle memory from the launch build. Everything in this guide is written against v0.111 beta, the August balance pass.
The best Doom showcase in the game is the Waterfall Giant, an Act 1b boss at 240 HP. Almost every action in the fight adds 3 Steam Eruption stacks; at 0 HP it turns invulnerable, clears all its debuffs, and self-destructs next turn for damage equal to those stacks, unless it is killed at 0 stacks, and the database names a Doom execute as the example of exactly that. In other words, this fight is designed to be stolen by your character: push Doom to threshold while the stack count sits at zero, let the end of turn execute delete the boss before the invulnerability phase and the explosion ever exist. For decks that must fight it straight up, the tip line notes Weak does not reduce the blast. Yours does not have to find out.
The Soul Loop: 0 Cost, Draw 2, Exhaust, and Why Boss Fights Starve
Souls are the lubricant of the class: 0 cost tokens that read draw 2 cards, then exhaust. The database describes them exactly that way, and the load-bearing word is exhaust. A Soul never stays in your deck. You play it, you see two new cards, it leaves the combat entirely. Reave is the pump: a 1 cost common attack that deals 9 damage, 11 upgraded, and shuffles 1 Soul into your draw pile, 2 upgraded. One upgraded Reave is 11 damage plus, across the next couple of turns, four extra cards seen, for one energy.
The payoff card is Haunt, a 1 cost uncommon power: whenever you play a Soul, a random enemy loses 6 HP, 8 upgraded. The database calls it the pivot of the S tier Soul engine, and the math is why. Each Soul is 0 cost draw 2. Under Haunt, each Soul is also a free 6 to 8 HP loss to a random enemy, which means your deck is thinning itself, cycling itself, and dealing damage all on the same free play. Once Haunt is online, every Reave is effectively 9 damage plus two mini nukes plus four cards of digging toward your next Scourge.
The self-thinning is the hidden mechanic. Souls exhaust out of your combat deck, so as the fight goes long your remaining library gets denser in the cards you actually want: Scourge, Unleash, Bodyguard. In short and medium fights this barely matters. In boss fights it is the difference between drawing your Doom stacker every turn and drawing it every third turn.
Now the warning the build database attaches to the whole archetype: balance Soul generation versus spending or you stall in boss fights. This is the number one Necrobinder loss pattern. Souls are finite fuel that burns on use, and a 12 turn boss fight will swallow every Soul a single Reave generated by turn 5. A hand of Haunt plus five basic cards and no Souls is a dead engine. The fix is drafting volume: take the second and third Reave, treat Soul generation as a primary need rather than a bonus, and hold Souls for turns where the two drawn cards actually matter rather than machine-gunning them all on turn one.
Co-op note: the v0.108 co-op card batch added Soulbound for this class, which links a teammate so your Souls enter their deck too. In a lobby, a Soul heavy Necrobinder is not just cycling itself, it is feeding an ally's hand, which is a large part of why the community slots this character into the board control role.
Act 1 Without the Engine: First Picks, Elites and Surviving on Weak and Poke
Act 1 is where Necrobinder runs are won and lost, because your execute is nearly useless here and your card pool is thin. Do the arithmetic once and it sticks: a Mawler has 72 HP, Scourge applies 13 Doom, and six Scourges is a dead Necrobinder long before it is a dead Mawler. Against 42 to 72 HP normals you win with damage and mitigation: Reave's 9 front-loaded damage, Poke's free 6, Unleash scaling off Osty, and Defy, a 1 cost Weak that the database flatly calls the best value mitigation in the game, cutting enemy attack damage by a quarter. Mawler's loop is 4 claws for 2 each into a 14 damage Tear, with a one time roar for 3 Vulnerable: Weak on the Tear turn, block or body-block the rest.
Card pick order for the first act, in sequence. Front-load damage and basics first: Reave, Poke, Defy. Then the Doom stackers as the act's elites approach: Scourge is the priority because it draws a card and never costs tempo, 13 Doom now, 16 upgraded. Save the powers, Haunt and Countdown, for when you already have fuel for them; a Haunt with no Souls in the deck is a 1 cost blank. End of Days is a rare that can wait for Act 2's swarms.
Elite prep differs by which Act 1 you rolled, and you should check the variant before pathing. Overgrowth offers Bygone Effigy at 127 HP cycling between asleep and awake, where the sleep phase is a free setup window for Osty and powers; Byrdonis at 91 HP alternating Dive and Peck, a Weak-on-Peck fight; and Phrog Parasite, which stuffs 3 Infection statuses into your discard and then spawns 4 stunned Wrigglers on death, with the fight only ending when all of them die, so you want AoE saved for phase two. Underdocks offers Skulking Colony at 79 HP with its per-hit damage cap, which Doom and multi-hit bypass cleanly; Terror Eel at 140 HP, one of the beefiest Act 1 elites, a straight staying power test where Osty body-blocking and Defy carry; and the four gardeners covered in the Osty section.
Two pathing facts from the patch history: since v0.101 floor 6 no longer spawns elites, so the early game is safer than older guides claim, and the classic rule still holds, path a rest site before your first elite. With 66 HP you cannot afford the Ironclad luxury of shrugging off a bad elite roll. If the boss is going to be Waterfall Giant or Lagavulin Matriarch, both of which reward long setup, an extra campfire upgrade on Scourge or Bodyguard is worth more than usual.
The Doom Package Ranked: Scourge, Countdown, Reaper Form and End of Days
Scourge first, and it is not close. One cost, apply 13 Doom, 16 upgraded, and draw a card, two upgraded. The database calls it the main Doom stacker that never costs tempo, and tempo is the entire argument: most Doom cards ask you to spend a card and get only Doom, but Scourge replaces itself, so your hand never shrinks while the bar fills. Take the first copy on sight, take the third copy in Act 2, upgrade it early. Multiples are the engine.
Countdown is the passive layer: a 1 cost uncommon power that applies 6 Doom, 9 upgraded, to a random enemy at the start of each turn. Ten turns of upgraded Countdown is 90 Doom for one card and one energy, absurd value, with two caveats. The target is random, so in multi enemy fights it smears rather than finishes, and it is slow, so it shines in exactly the long grindy fights this class ends up in anyway. The special case worth memorizing: Countdown keeps ticking during Ceremonial Beast's Ringing phase, when you may only play one card per turn. Passive Doom is one of the few mechanics in the game that answers a card cap by not playing cards at all.
Reaper Form is the ceiling: a 3 cost rare power where whenever your attacks deal damage, you apply that much Doom. Read it again with your card pool in mind. Reave becomes 9 damage and 9 Doom. Poke becomes 6 and 6. Unleash converts its full Osty hit, including the Osty HP bonus, into Doom. The database describes it as the ceiling card of Doom times attack hybrid decks, and it solves the class's core math problem, which is that pure Doom stackers are too slow for 252 HP bosses. Under Reaper Form, your entire damage package doubles as your execute package.
End of Days is the finisher: a 3 cost rare attack with massive AoE Doom that immediately executes enemies at threshold. The word immediately matters, because it does not wait for end of turn, so this is the card that deletes a board the moment the bar fills, and the database notes it can end fights on the spot. The site's Doom build core lists it alongside Blight Strike and a Soul engine, and that is the template draft: stackers, one big AoE finisher, and the Soul loop that finds both. In Act 2, against Infested Prism's 200 HP or Entomancer's endless bees, End of Days is the difference between a clean sweep and a six turn slog.
Boss Playbook: Six Early Bosses and Which Ones Doom Deletes
Vantom, Act 1a, 173 HP. It opens with 9 Slippery stacks, so every hit deals exactly 1 damage, and it runs a fixed 4-turn loop where turn 3 is a 25-plus killer swing and turn 4 is a self-buff turn, your window. Cheap multi-hit attacks strip the stacks; Osty and Unleash are nearly useless into the wall. The Necrobinder line is to Weak or full-block turn 3, let Doom accumulate quietly, and treat turn 4 as a free setup turn rather than a damage race.
The Kin, Act 1a, 190 plus two acolytes around 58 each. The acolytes hit hard and scale Strength while the priest debuffs from the backline, and the correct order is acolytes first, priest last. Doom's threshold model rewards focused single target pressure, Scourge into one acolyte until it executes, while Osty body-blocks the other and Defy blunts the priest.
Ceremonial Beast, Act 1a, 252 HP. It gains +2 Strength every turn, a pure damage race, and below 150 HP it staggers into Ringing, where you may play only one card per turn. Plan the threshold deliberately: arrive near 150 with Doom already banked, then spend Ringing turns playing your single best card, usually Scourge or Bodyguard, while Countdown ticks and the end of turn execute approaches. Pushing it below 150 with no Doom on board is how you lose this fight.
Soul Fysh, Act 1b, 211 HP. It stuffs Beckon statuses into your deck, 1 cost cards that deal 6 unblockable damage if left unplayed, and gains Intangible on turns 4 and 5. Your Souls are the answer: 0 cost draw 2 digs you to Beckons faster than any other class can, so play them, and defend through the Intangible turns instead of attacking into them.
Waterfall Giant, Act 1b, 240 HP. Covered in the rules section, but the summary: actions add 3 Steam Eruption stacks, at 0 HP it goes invulnerable, clears debuffs and detonates next turn for stack damage, unless killed at 0 stacks, which a Doom execute does cleanly. Do not bother with Weak, it does not reduce the blast. Race the threshold instead.
Lagavulin Matriarch, Act 1b, 222 HP, starts asleep and gets worse the longer the fight runs. Sleep is your setup window: Osty HP, Haunt, Countdown, and a big Doom head start, then wake it near threshold. And when you reach Act 2, respect the Insatiable: its Sandpit death timer starts at 4 and hitting zero ends the run, so always play the Frantic Escape cards and never exhaust cards carelessly, which tempers your Soul usage in that one fight.
Relic Priority: Beating Remnant, Diamond Diadem and the Stall Package
The deck wants to stretch fights, so the relic shortlist is a stall package. Beating Remnant is the headline: a rare that caps your HP loss at 20 per turn, anti-one-shot insurance at high Ascension, and the site's synergy page explicitly pairs it with Doom Execute to stall safely to threshold. Once you can only lose 20 HP per turn, every long fight becomes a solvable math problem: keep Osty alive, keep stacking, and the execute arrives before your body fails.
Diamond Diadem, an Ancient blessing, rewards the turtle turns directly: if you play 2 or fewer cards in a turn, you take half damage from enemies. This class can genuinely do that. Bound Phylactery summons without a card, Countdown applies Doom without a card, and end of turn executes happen without a card, so your safest turns are often your lowest-play turns. Sai, the Ancient granting 7 Block at the start of each turn, sits near the top of the community ladder at a 92.3 percent win rate, and Anchor, 10 Block at combat start, is plain but always online. Together they patch the 66 HP problem from two directions.
Boss-fight sustain matters more for you than for most, because your fights run long. Pantograph heals 25 HP at the start of boss combats, a massive error margin for this character. Red Mask applies 1 Weak to all enemies at combat start, a quarter off every incoming attack for free, and Bag of Marbles is the offensive mirror with 1 Vulnerable for your Reave and Unleash turns.
Board-fight relics pair with End of Days. Gremlin Horn, consensus S tier, grants 1 energy and 1 card whenever an enemy dies, and an AoE Doom finisher that executes a whole board converts directly into a burst of fuel for the follow-up turn. Mercury Hourglass adds 3 damage to all enemies at the start of your turn, quietly shortening every elite fight by two turns.
Consistency picks: Bag of Preparation draws 2 extra on turn one so you actually open with Bodyguard or Scourge; Lantern adds an energy on the first turn; Ice Cream conserves energy between turns if you want big Soul-dump turns; Gambling Chip lets you sculpt the opening hand at every combat start. One hard avoid: Ancient blessings priced with an Affliction. Afflictions replace curses by attaching debuffs to your existing cards, and they cannot be shop-removed, so a Soul-hungry engine deck cannot afford a single polluted draw. The site gives thin-deck Claw builds the same warning for the same reason.
Five Ways Necrobinder Runs Die (and the Fixes)
One: Soul starvation in boss fights. The build database warning is explicit, balance Soul generation versus spending or you stall in boss fights. Souls exhaust on use, so long fights drain the tank, and a Haunt with nothing to feed it is a dead power. Draft volume: second and third Reave, the upgrade that makes it shuffle 2 Souls, and the discipline to save Souls for turns where the drawn cards matter.
Two: importing Poison logic. Doom does not tick. A stack count below max HP is worth exactly nothing at end of turn, and a stack count above it is worth exactly one kill. Before playing a Doom card, look at the enemy HP bar, and once the threshold is mathematically reached, stop spending on Doom entirely and pivot the rest of the turn to Osty, Souls, or defense.
Three: letting Osty starve. Unleash reads 6 plus current Osty HP. If you never re-summon, your signature attack decays into a bad Strike while your body-blocker thins out. Bodyguard stays a real card in the mid-game rotation; it is not Act 1 filler you outgrow once the shiny rares arrive.
Four: playing like you have Ironclad HP. You have 66. A fight you win at 20 HP remaining is a fight you lose two floors later. Defy is your healing, in the sense that a quarter off every enemy attack across a run is worth more than most heals, and the campfire question leans rest over upgrade more often for you than the general site advice for tankier characters.
Five: matchup-specific traps. The Insatiable's Sandpit timer punishes careless exhaust, so meter your Souls there. Skulking Colony's per-hit cap neuters Unleash, so lean on Doom and multi-hit. Vantom's Slippery makes Osty nearly irrelevant, so lean on Doom. Waterfall Giant punishes slow damage decks with the detonation, so race the threshold early rather than building toward a turn 12 execute.
In co-op, your role is board control: Osty soaks hits for the team, Soulbound feeds an ally's deck, and your percentage execute is the answer to HP pools that scale to four or five times normal while attack damage stays flat. Keep the tankiest player alive per the community iron rule, funnel defensive potions to them when the team is low, and remember enemy Block also scales in multiplayer even though damage does not. Your Doom threshold becomes the team's win condition in every boss lobby that would otherwise be an HP wall.