Phase 4: 10 boss-exclusive legendaries + ammo/HP balance fixes

Legendaries (cap 1, boss-only): Butcher's Oath, Second Skin, Twin Sidearm,
Crimson Metronome, Abattoir Engine, Gore Crown, Thousand Teeth, Hollow Father,
The Last Cut, Meat Grinder. Once-per-floor flags reset in nextFloor.

Balance fixes: Ghoul Heart now +4 HP (2 full hearts); Brass Magazine ammo
efficiency uses the same diminishing additive formula as Scrap Feed.

docs/items.md

@@ -109,7 +109,7 @@ All of these trigger from your weapon hits (orbital knives proc at half chance).
 | Item | Description | Exact effect per tier |
 |---|---|---|
 | **Iron Stomach** | +½ heart container, heal ½ heart | `maxHp +1`, heal 1 |
-| **Ghoul Heart** | +2 max HP, heal 2 | `maxHp +2`, heal 2 |
+| **Ghoul Heart** | +4 max HP, heal 4 | `maxHp +4`, heal 4 — a full 2 hearts |
 | **Twin Hearts** | +1 max heart, heal to full | `maxHp +2`, `hp = maxHp` — the premium Rare HP item |
 | **Rendered Fat** | +½ heart, +4% armor | `maxHp +1`, `armor +0.04`, heal 1 — clean hybrid HP/armor |
 | **Gristle Cord** | +0.12s hurt immunity, +4% armor | `invBonus +0.12`, `armor +0.04` |
@@ -139,7 +139,7 @@ All of these trigger from your weapon hits (orbital knives proc at half chance).
 | **Magnet Maw** | +60% pickup radius | `magnet ×1.6` — magnet radius 46 × magnet px |
 | **Gorging Leech** | +20% XP gained | `xpMul ×1.20` |
 | **Reroll Rib** | +1 perk reroll each level | `rerollPerLevel +1` and +1 reroll immediately |
-| **Brass Magazine** | 15% less ammo use, +20% ammo found | `ammoEff ×1.15`, `ammoPickupMul ×1.20` (the ×1.15 stays multiplicative; the **Scrap Feed** perk's additive stacks sit underneath it) |
+| **Brass Magazine** | +10% ammo efficiency, +20% ammo found | `ammoEff +0.10` (same diminishing additive formula as **Scrap Feed**, so the saving never reaches 50%), `ammoPickupMul ×1.20` |
 | **Hollow Bones** | +14% move speed | `speedMul ×1.14` (178 → ~203 px/s at tier I) |
 | **Gorged Tick** | +15% XP, +10% luck | `xpMul ×1.15`, `luck +0.10` |
 | **Hooked Sinew** | +30% pickup pull speed, +10% radius | `magnetPull ×1.30`, `magnet ×1.10` (activates the `magnetPull` stat) |
@@ -224,6 +224,16 @@ All of these trigger from your weapon hits (orbital knives proc at half chance).
 | 70 | Sawbone Coil | Uncommon | V | Shot modifier |
 | 71 | Slaughter Rhythm | Rare | III | Fire rate |
 | 72 | Thresher Plate | Uncommon | V | Survivability |
+| 73 | Abattoir Engine | Legendary | I | Utility |
+| 74 | Butcher's Oath | Legendary | I | Damage |
+| 75 | Crimson Metronome | Legendary | I | Fire rate |
+| 76 | Gore Crown | Legendary | I | On-kill |
+| 77 | Hollow Father | Legendary | I | Utility |
+| 78 | Meat Grinder | Legendary | I | Survivability |
+| 79 | Second Skin | Legendary | I | Survivability |
+| 80 | The Last Cut | Legendary | I | Damage |
+| 81 | Thousand Teeth | Legendary | I | Shot modifier |
+| 82 | Twin Sidearm | Legendary | I | Shot modifier |
 
 ## Synergy notes
 

js/enemies.js

@@ -148,6 +148,23 @@ function procOnHit(e, dmg, ang, opts) {
   const magnitudeScale = opts.procMagnitudeScale === undefined ? 1 : opts.procMagnitudeScale;
   const intervalScale = opts.procIntervalScale === undefined ? 1 : opts.procIntervalScale;
   const procDamage = dmg / Math.max(0.05, intervalScale) * magnitudeScale;
+  // Thousand Teeth: bullets shatter into 6 extra shards that can crit.
+  // Shards inherit the shard flag so they don't recurse. The −40% base bullet
+  // damage is applied as a global dmgMul penalty in the item's apply().
+  if (s.thousandTeeth > 0 && !(opts.bullet && opts.bullet.shard) && chance(clamp(chanceScale, 0, 1))) {
+    for (let i = 0; i < 6; i++) {
+      const sa = rand(0, TAU);
+      const shardCrit = chance(s.crit || 0);
+      G.bullets.push({
+        x: e.x, y: e.y, ang: sa,
+        vx: Math.cos(sa) * 300 * s.shotSpeedMul, vy: Math.sin(sa) * 300 * s.shotSpeedMul,
+        r: 3 * s.sizeMul, dmg: procDamage * 0.4 * (shardCrit ? (s.critMul || 2) : 1), pierce: 0, bounce: s.bounce,
+        life: 0.35 * s.rangeMul, t: 0, behavior: 'bullet', sprite: 'bullet_bone',
+        homing: s.homing ? 1.6 + s.homing * 0.7 : 0, shard: true, sizeMul: s.sizeMul,
+      });
+    }
+    spawnSpark(e.x, e.y, ang);
+  }
   if (s.splinter > 0 && !(opts.bullet && opts.bullet.shard) && chance(clamp(chanceScale, 0, 1))) {
     const count = Math.min(18, Math.floor(s.splinter));
     for (let i = 0; i < count; i++) {
@@ -241,6 +258,12 @@ function killEnemy(e, ang) {
 
   if (e.boss) { onBossDeath(e); return; }
 
+  // Gore Crown: free nova on every kill
+  if (p.stats.goreCrown > 0) {
+    areaDamage(e.x, e.y, 70 * Math.sqrt(p.stats.sizeMul), 8 * p.stats.dmgMul * p.stats.dmgLiveMul, true, { noProc: true, noCrit: true });
+    spawnExplosionFx(e.x, e.y, 60);
+  }
+
   // Blood Moat: kills leave an acid pool
   if (p.stats.bloodMoat > 0 && G.hazards.length < 80) {
     G.hazards.push({ kind: 'acid', x: e.x, y: e.y, r: 16 * p.stats.sizeMul, life: 2.5, t: 0, dps: 5 * p.stats.dmgMul * p.stats.dmgLiveMul });

js/items.js

@@ -21,7 +21,7 @@ const ITEMS = {
   magnetmaw:     { name: 'Magnet Maw',       desc: '+60% pickup radius',          rarity: 'common', cap: 3, apply: s => { s.magnet *= 1.6; } },
   gorgingleech:  { name: 'Gorging Leech',    desc: '+20% XP gained',              rarity: 'common', cap: 4, apply: s => { s.xpMul *= 1.20; } },
   hollowbones:   { name: 'Hollow Bones',     desc: '+14% move speed',             rarity: 'common', cap: 6, apply: s => { s.speedMul *= 1.14; } },
-  brassmagazine: { name: 'Brass Magazine',   desc: '15% less ammo use, +20% ammo found', rarity: 'common', cap: 5, apply: s => { s.ammoEff *= 1.15; s.ammoPickupMul *= 1.20; } },
+  brassmagazine: { name: 'Brass Magazine',   desc: '+10% ammo efficiency, +20% ammo found', rarity: 'common', cap: 5, apply: s => { s.ammoEff += 0.10; s.ammoPickupMul *= 1.20; } },
   ironstomach:   { name: 'Iron Stomach',     desc: '+½ heart container, heal ½ heart', rarity: 'common', cap: 8, apply: (s, p) => { s.maxHp += 1; p.hp = Math.min(s.maxHp, p.hp + 1); } },
   tannedhide:    { name: 'Tanned Hide',      desc: '+8% chance to ignore damage', rarity: 'common', cap: 6, apply: s => { s.armor += 0.08 / 0.92; } },
   bloodlust:     { name: 'Bloodlust',        desc: 'Kills may drop bonus XP',     rarity: 'common', cap: 5, apply: s => { s.bloodlust = (s.bloodlust || 0) + 0.12; } },
@@ -43,7 +43,7 @@ const ITEMS = {
   spinecage:     { name: 'Spine Cage',       desc: 'Contact attackers take damage', rarity: 'uncommon', cap: 5, apply: s => { s.thorns += 8; } },
   spitewell:     { name: 'Spite Well',       desc: 'Taking damage releases a blood nova', rarity: 'uncommon', cap: 5, apply: s => { s.retaliate += 10; } },
   orbitcrown:    { name: 'Orbit Crown',      desc: '+25% orbital speed and damage', rarity: 'uncommon', cap: 5, apply: s => { s.orbSpeedMul *= 1.25; s.orbDmgMul *= 1.25; } },
-  ghoulheart:    { name: 'Ghoul Heart',      desc: '+2 max HP, heal 2',           rarity: 'uncommon', cap: 5, apply: (s, p) => { s.maxHp += 2; p.hp = Math.min(s.maxHp, p.hp + 2); } },
+  ghoulheart:    { name: 'Ghoul Heart',      desc: '+4 max HP, heal 4',           rarity: 'uncommon', cap: 5, apply: (s, p) => { s.maxHp += 4; p.hp = Math.min(s.maxHp, p.hp + 4); } },
 
   // ---- rare ----
   splittongue:   { name: 'Split Tongue',     desc: 'Twin parallel shot',          rarity: 'rare', cap: 3, apply: s => { s.split += 1; } },
@@ -89,6 +89,18 @@ const ITEMS = {
   ironlung:      { name: 'Iron Lung',        desc: 'The first hit each room is blocked', rarity: 'rare', cap: 3, apply: s => { s.ironLung += 1; } },
   meathook:      { name: 'Meat Hook',        desc: 'Kills yank nearby enemies to the corpse', rarity: 'uncommon', cap: 4, apply: s => { s.meatHook += 1; } },
   blooddebt:     { name: 'Blood Debt',       desc: '+35% damage, −½ heart container', rarity: 'rare', cap: 3, apply: (s, p) => { s.dmgMul *= 1.35; s.maxHp = Math.max(1, s.maxHp - 1); p.hp = Math.min(p.hp, s.maxHp); } },
+
+  // ---- phase 4: boss-exclusive legendaries (cap 1, curses allowed) ----
+  butchersoath:  { name: "Butcher's Oath",   desc: '+80% damage, but max HP set to 2', rarity: 'legendary', cap: 1, apply: (s, p) => { s.dmgMul *= 1.8; s.maxHp = Math.min(s.maxHp, 2); p.hp = Math.min(p.hp, s.maxHp); } },
+  secondskin:    { name: 'Second Skin',      desc: 'Revive once per floor at ½ heart', rarity: 'legendary', cap: 1, apply: s => { s.secondSkin += 1; } },
+  twinsidearm:   { name: 'Twin Sidearm',     desc: 'Bone Popper double-taps; specials burn 2× ammo', rarity: 'legendary', cap: 1, apply: s => { s.twinSidearm += 1; } },
+  crimsonmetronome:{ name: 'Crimson Metronome', desc: '+60% fire rate; every 8th shot costs ½ heart', rarity: 'legendary', cap: 1, apply: s => { s.rateMul *= 1.6; s.crimsonMetronome += 1; } },
+  abattoirengine:{ name: 'Abattoir Engine',  desc: 'Pressure rises 2× faster; score and luck ×1.5', rarity: 'legendary', cap: 1, apply: s => { s.abattoirEngine += 1; s.luck += 0.5; } },
+  gorecrown:     { name: 'Gore Crown',       desc: 'Free nova on every kill, −25% damage', rarity: 'legendary', cap: 1, apply: s => { s.goreCrown += 1; s.dmgMul *= 0.75; } },
+  thousandteeth: { name: 'Thousand Teeth',   desc: '+6 shards that can crit, −40% base bullet damage', rarity: 'legendary', cap: 1, apply: s => { s.thousandTeeth += 1; s.dmgMul *= 0.6; } },
+  hollowfather:  { name: 'Hollow Father',    desc: '3 damage-scaling orbitals, −25% fire rate', rarity: 'legendary', cap: 1, apply: s => { s.orbitals += 3; s.hollowFather += 1; s.rateMul *= 0.75; } },
+  thelastcut:    { name: 'The Last Cut',     desc: 'At ½ heart: ×3 damage, +1s immunity', rarity: 'legendary', cap: 1, apply: s => { s.theLastCut += 1; } },
+  meatgrinder:   { name: 'Meat Grinder',     desc: '12 dps aura within 90px, +1 damage taken per hit', rarity: 'legendary', cap: 1, apply: s => { s.meatGrinder += 1; } },
 };
 
 const ITEM_LEVEL_CAP = 9;

js/player.js

@@ -26,6 +26,9 @@ function initPlayer() {
       dmgLiveMul: 1, executeBonus: 0, burnDamageBonus: 0, choirEvery: 0, sawboneCoil: 0,
       gluttonGut: 0, slaughterRhythm: 0, painEngine: 0, thresherPlate: 0, bloodMoat: 0,
       ironLung: 0, meatHook: 0, bloodDebt: 0,
+      // phase-4 legendaries
+      secondSkin: 0, twinSidearm: 0, crimsonMetronome: 0, abattoirEngine: 0,
+      goreCrown: 0, thousandTeeth: 0, hollowFather: 0, theLastCut: 0, meatGrinder: 0,
       maxHp: 6,
     },
   };
@@ -127,16 +130,23 @@ function updatePlayer(dt) {
   } else {
     if (Input.mdown && p.fireT <= 0 && p.weapon.ammo > 0) {
       fireWeapon(p, w);
+      // Twin Sidearm: the Bone Popper double-taps
+      if (st.twinSidearm > 0 && p.weapon.id === 'bonepopper') fireWeapon(p, w);
       // Hollow Choir: every 4th shot fires a free extra volley
       if (st.choirEvery > 0) {
         p.choirCount = (p.choirCount || 0) + 1;
         if (p.choirCount >= 4) { p.choirCount = 0; fireWeapon(p, w); }
       }
+      // Crimson Metronome: every 8th shot costs ½ heart
+      if (st.crimsonMetronome > 0) {
+        p.metronomeCount = (p.metronomeCount || 0) + 1;
+        if (p.metronomeCount >= 8) { p.metronomeCount = 0; p.hp = Math.max(0.5, p.hp - 1); spawnText(p.x, p.y - 14, '-½', '#e2472f'); }
+      }
       p.recoil = Math.min(1, p.recoil + (w.behavior === 'slam' ? 1 : 0.45));
       p.muzzleT = 0.07;
       p.attackT = 0.4; p.actionT = 0;
       p.fireT = rate;
-      if (p.weapon.ammo !== Infinity) p.weapon.ammo -= 1 / st.ammoEff;
+      if (p.weapon.ammo !== Infinity) p.weapon.ammo -= (st.twinSidearm > 0 ? 2 : 1) / st.ammoEff;
       Sfx.shoot(w);
       if (w.behavior === 'slam') addShake(5);
     }
@@ -182,6 +192,23 @@ function updatePlayer(dt) {
   st.rhythmRateBonus = rhythm;
   if (p.painEngineT > 0) p.painEngineT -= dt;
   st.dmgLiveMul = p.painEngineT > 0 ? 1 + st.painEngine : 1;
+  // The Last Cut: while at ½ heart, ×3 damage
+  if (st.theLastCut > 0 && p.lastCutActive && p.hp <= 1) st.dmgLiveMul *= 3;
+
+  // Meat Grinder: passive 12 dps aura within 90px
+  if (st.meatGrinder > 0) {
+    p.meatGrinderTick = (p.meatGrinderTick || 0) - dt;
+    if (p.meatGrinderTick <= 0) {
+      p.meatGrinderTick = 0.5;
+      for (const e of G.enemies) {
+        if (e.hp <= 0) continue;
+        if (dist2(e.x, e.y, p.x, p.y) < (90 + e.r) * (90 + e.r)) {
+          tickEnemyDamage(e, 6 * st.dmgMul * st.dmgLiveMul);
+          if (chance(0.3)) spawnBlood(e.x, e.y, angleTo(p.x, p.y, e.x, e.y), 2);
+        }
+      }
+    }
+  }
 
   // Thresher Plate: passive contact-damage aura (no need to be hit)
   if (st.thresherPlate > 0) {
@@ -232,6 +259,8 @@ function hurtPlayer(dmg, ang, attacker) {
     return;
   }
   let reduced = Math.max(1, Math.round(dmg));
+  // Meat Grinder: aura damages you for +1 per hit taken
+  if (p.stats.meatGrinder > 0) reduced += p.stats.meatGrinder;
   // shield hearts absorb first (from the Shield Heart perk)
   if (p.shieldHp > 0) {
     const absorbed = Math.min(p.shieldHp, reduced);
@@ -262,7 +291,27 @@ function hurtPlayer(dmg, ang, attacker) {
     areaDamage(p.x, p.y, 85 * Math.sqrt(p.stats.sizeMul), p.stats.retaliate * p.stats.dmgMul, true, { noProc: true });
     spawnExplosionFx(p.x, p.y, 70);
   }
+  // The Last Cut: at the brink, gain ×3 damage and +1s immunity
+  if (p.stats.theLastCut > 0 && p.hp > 0 && p.hp <= 1 && !p.lastCutActive) {
+    p.lastCutActive = true;
+    p.invT = Math.max(p.invT, 1.0 + p.stats.invBonus);
+    spawnText(p.x, p.y - 20, 'THE LAST CUT', '#e2472f');
+    addToast('THE LAST CUT', '×3 damage while at ½ heart');
+    Sfx.shieldUp();
+  }
   if (p.hp <= 0) {
+    // Second Skin: revive once per floor at ½ heart
+    if (p.stats.secondSkin > 0 && !p.secondSkinUsed) {
+      p.secondSkinUsed = true;
+      p.hp = 1;
+      p.invT = 1.5;
+      G.flash = 0.6;
+      addShake(10);
+      spawnText(p.x, p.y - 20, 'SECOND SKIN', '#e2472f');
+      addToast('SECOND SKIN', 'you refuse to die — once per floor');
+      Sfx.shieldUp();
+      return;
+    }
     p.hp = 0;
     p.deathT = 0;
     gameOver();

js/rooms.js

@@ -200,6 +200,9 @@ function nextFloor() {
   // Shield Heart perk: fresh shield hearts each floor
   G.player.shieldHp = G.player.stats.shieldPerk || 0;
   if (G.player.shieldHp > 0) { spawnText(G.player.x, G.player.y - 20, 'SHIELD UP', '#3bc9e0'); Sfx.shieldUp(); }
+  // legendary once-per-floor flags reset
+  G.player.secondSkinUsed = false;
+  G.player.lastCutActive = false;
   G.player.x = W / 2; G.player.y = H / 2;
   addToast('FLOOR ' + G.floor, 'the meat runs deeper here');
   Music.requestFloorMusic();

js/sprites.js

@@ -42,6 +42,8 @@ const SPRITE_MANIFEST = [
   'i_deadweight', 'i_cauterizedveins', 'i_hollowchoir', 'i_sawbonecoil', 'i_gluttonsgut',
   'i_slaughterrhythm', 'i_painengine', 'i_thresherplate', 'i_bloodmoat', 'i_ironlung',
   'i_meathook', 'i_blooddebt',
+  'i_butchersoath', 'i_secondskin', 'i_twinsidearm', 'i_crimsonmetronome', 'i_abattoirengine',
+  'i_gorecrown', 'i_thousandteeth', 'i_hollowfather', 'i_thelastcut', 'i_meatgrinder',
   // full 64px/128px eight-direction action atlases
   'player_sheet', 'player_legs_sheet',
   'enemy_shambler_sheet', 'enemy_runner_sheet', 'enemy_spitter_sheet',

js/state.js

@@ -55,7 +55,7 @@ const PRESSURE_DIAL_MIN = -5, PRESSURE_DIAL_MAX = 5;
 function pressureGainUnits(dial) { const d = clamp(dial, PRESSURE_DIAL_MIN, PRESSURE_DIAL_MAX); return d <= 0 ? 1 + d * 0.2 : 1 + d * 0.8; }
 // -5 -> 5 units, 0 -> 3 units, +5 -> 0 units (piecewise linear)
 function pressureDropUnits(dial) { const d = clamp(dial, PRESSURE_DIAL_MIN, PRESSURE_DIAL_MAX); return d <= 0 ? 3 - d * 0.4 : 3 - d * 0.6; }
-function pressureGain()      { return pressureGainUnits(G.pressureDial) * PRESSURE_UNIT; }
+function pressureGain()      { const base = pressureGainUnits(G.pressureDial) * PRESSURE_UNIT; return base * (G.player && G.player.stats.abattoirEngine > 0 ? 2 : 1); }
 function pressureDropScale() { return pressureDropUnits(G.pressureDial) / PRESSURE_DROP_BASE; }
 
 // total player power: perks drafted (level - 1) + item tiers owned, weighted by rarity.

test/smoke.js

@@ -318,9 +318,9 @@ step(30, 16);
 
 console.log('== expanded perk and item rosters ==');
 {
-  check('41 new items added (14 phase-2 + 12 phase-3 passives)', Object.keys(ctx.ITEMS).length === 72);
+  check('41 new items added (14 phase-2 + 12 phase-3 + 10 legendaries)', Object.keys(ctx.ITEMS).length === 82);
   const newPerks = ['critbone', 'critmeat', 'flensing', 'ember', 'frostbile', 'heavyhand', 'thickhide', 'secondwind', 'scrapfeed', 'boneknit', 'spiteflesh', 'carrion', 'sinew'];
-  const newItems = ['chainsinew', 'mortarbone', 'bloatrounds', 'marrowglut', 'hollowneedle', 'bloodshoteye', 'flayerkiss', 'emberjar', 'acidgland', 'hookrounds', 'sledgerounds', 'graftedtrigger', 'deadmanswitch', 'orbitcrown', 'tannedhide', 'deadmansclock', 'hollowbones', 'boneplate', 'wormgut', 'spinecage', 'secondstomach', 'spitewell', 'twinhearts', 'brassmagazine', 'crowbait', 'gorgingleech', 'rerollrib', 'chillgland', 'hookedsinew', 'gyroscopicribs', 'marrowpiston', 'splitcortex', 'gristlecord', 'renderedfat', 'whipcordtendon', 'rusteddiadem', 'gorgedtick', 'bonemealpowder', 'rimedfang', 'butcherstwine', 'cindersump', 'deadweight', 'cauterizedveins', 'hollowchoir', 'sawbonecoil', 'gluttonsgut', 'slaughterrhythm', 'painengine', 'thresherplate', 'bloodmoat', 'ironlung', 'meathook', 'blooddebt'];
+  const newItems = ['chainsinew', 'mortarbone', 'bloatrounds', 'marrowglut', 'hollowneedle', 'bloodshoteye', 'flayerkiss', 'emberjar', 'acidgland', 'hookrounds', 'sledgerounds', 'graftedtrigger', 'deadmanswitch', 'orbitcrown', 'tannedhide', 'deadmansclock', 'hollowbones', 'boneplate', 'wormgut', 'spinecage', 'secondstomach', 'spitewell', 'twinhearts', 'brassmagazine', 'crowbait', 'gorgingleech', 'rerollrib', 'chillgland', 'hookedsinew', 'gyroscopicribs', 'marrowpiston', 'splitcortex', 'gristlecord', 'renderedfat', 'whipcordtendon', 'rusteddiadem', 'gorgedtick', 'bonemealpowder', 'rimedfang', 'butcherstwine', 'cindersump', 'deadweight', 'cauterizedveins', 'hollowchoir', 'sawbonecoil', 'gluttonsgut', 'slaughterrhythm', 'painengine', 'thresherplate', 'bloodmoat', 'ironlung', 'meathook', 'blooddebt', 'butchersoath', 'secondskin', 'twinsidearm', 'crimsonmetronome', 'abattoirengine', 'gorecrown', 'thousandteeth', 'hollowfather', 'thelastcut', 'meatgrinder'];
   check('all new perks have manifest icons or fallbacks', newPerks.every(id => ctx.SPRITE_MANIFEST.includes('perk_' + id)));
   check('all new items have manifest icons or fallbacks', newItems.every(id => ctx.SPRITE_MANIFEST.includes('i_' + id)));
   check('new roster entries all have names, descriptions and effects',
@@ -367,10 +367,13 @@ console.log('== scrap feed has diminishing returns (like thick hide) ==');
   check('first stack ~5% saving', Math.abs(s1 - (1 - 1 / 1.05)) < 0.0001);
   check('each stack helps less', d2 < d1 && d3 < d2);
   check('saving never reaches 100%', save() < 1);
-  // Brass Magazine still multiplies on top (unchanged)
+  // Brass Magazine uses the same diminishing additive formula as Scrap Feed
   const s2x = { ammoEff: 1, ammoPickupMul: 1 };
   ctx.ITEMS.brassmagazine.apply(s2x, {});
-  check('brass magazine stays multiplicative', Math.abs(s2x.ammoEff - 1.15) < 0.0001);
+  check('brass magazine is additive-diminishing (not multiplicative)', Math.abs(s2x.ammoEff - 1.10) < 0.0001);
+  const s2y = { ammoEff: 1, ammoPickupMul: 1 };
+  for (let i = 0; i < 5; i++) ctx.ITEMS.brassmagazine.apply(s2y, {});
+  check('brass magazine never reaches 50% saving', 1 - 1 / s2y.ammoEff < 0.5);
 }
 
 console.log('== close-range weapon impact pass ==');
@@ -498,6 +501,33 @@ console.log('== tier-scaled items + duplicate favoring ==');
   check('item rolls favor owned items (' + ownedHits + '/200)', ownedHits >= 40);
 }
 
+console.log('== phase-4 boss-exclusive legendaries ==');
+{
+  const p = ctx.G.player;
+  p.items = {};
+  // boss pool is the only source that can roll legendaries
+  let bossLegendaries = 0;
+  for (let i = 0; i < 400; i++) if (ctx.ITEMS[ctx.rollItemId('boss', 5)].rarity === 'legendary') bossLegendaries++;
+  check('boss pool can roll legendaries (' + bossLegendaries + '/400)', bossLegendaries > 10);
+  // Butcher's Oath: big damage, HP clamped to 2
+  const savedMax = p.stats.maxHp, savedHp = p.hp;
+  p.stats.maxHp = 10; p.hp = 10;
+  ctx.giveItem('butchersoath');
+  check('Butcher\'s Oath clamps max HP to 2', p.stats.maxHp === 2 && p.hp === 2);
+  p.stats.maxHp = savedMax; p.hp = savedHp; delete p.items.butchersoath;
+  // Second Skin: revive once per floor at ½ heart
+  p.stats.secondSkin = 0; p.secondSkinUsed = false;
+  ctx.giveItem('secondskin');
+  p.hp = 1; p.invT = 0; ctx.G.mode = 'play';
+  ctx.hurtPlayer(9999, 0);
+  check('Second Skin revives at ½ heart', p.hp === 1 && p.secondSkinUsed === true && ctx.G.mode === 'play');
+  // second death same floor is real
+  p.invT = 0;
+  ctx.hurtPlayer(9999, 0);
+  check('Second Skin only works once per floor', ctx.G.mode === 'gameover');
+  ctx.startRun(); step(3, 16);
+}
+
 console.log('== phase-3 hook passives ==');
 {
   const p = ctx.G.player;
@@ -984,7 +1014,7 @@ console.log('== item stickiness ramps with owned count ==');
 
 console.log('== help manual grows with the implant roster ==');
 {
-  check('10 help pages (4 implant pages for 72 items)', ctx.HELP_PAGES.length === 10);
+  check('10 help pages (4 implant pages for 82 items)', ctx.HELP_PAGES.length === 10);
   check('10 help renderers', ctx.HELP_RENDERERS.length === 10);
   ctx.G.player = ctx.G.player || {};
   const fctx = fakeCtx();

tools/gen_assets.py

@@ -291,6 +291,16 @@ ITEMS = {
     "ironlung": "a riveted iron lung with bellows and a steel windpipe",
     "meathook": "a huge rusted slaughterhouse meat hook on a taut chain",
     "blooddebt": "a parchment contract signed in blood with a heart seal",
+    "butchersoath": "a blood-soaked butcher cleaver crossed with a black oath scroll",
+    "secondskin": "a pale translucent second skin peeling away to reveal muscle",
+    "twinsidearm": "two crossed bone pistols fused at the grip with sinew",
+    "crimsonmetronome": "a crimson metronome with a heart-shaped pendulum and blood drips",
+    "abattoirengine": "a roaring industrial abattoir engine with pressure gauges and meat grinders",
+    "gorecrown": "a jagged crown of congealed blood and bone spikes radiating a red aura",
+    "thousandteeth": "a gaping maw with hundreds of tiny sharp teeth in concentric rings",
+    "hollowfather": "a gaunt hollow patriarch figure with three orbiting bone halos",
+    "thelastcut": "a single gleaming cleaver edge with a desperate red gleam",
+    "meatgrinder": "an industrial meat grinder with spinning blades and gore pouring through",
 }
 for iid, subject in ITEMS.items():
     SPECS["i_" + iid] = Spec(subject + ", isolated inventory object, strong top-left light, no medallion, no icon background", 32)