Phase 5C (rosters): T3 polish + feywild T4-spread fix

Phase 5-B's exit named two follow-ups: T3 below band (manor 39 /
underforge 47 vs 55-75) and the T4 spread (feywild 59 vs underdark
88, 30pp asymmetry). Phase 5-C re-runs the Phase 4-A trace on the
four affected zones under the shipped Phase 5-B cell and applies
roster knobs only (IsElite + SpawnWeight; no bestiary stat-block
touches).

TestExpeditionBalance_Phase5C_OutlierDiagnostic names the killer
per zone:

  manor_blackspire (53%): Vampire Spawn (72% win, 42 kills) +
    Revenant (16% win, 31 kills at SW=1, can't go lower). First
    attempt trimmed VS SW 3 -> 2 and backfired by concentrating
    elite share on Revenant (kills jumped to 48); reverted.
  underforge (49.5%): Fire Elemental (57 kills, 61hp/win) +
    Salamander (33 kills) carry the lethality; Helmed Horror only
    100%-win elite but SW=1, no dilution effect.
  feywild_crossing (54%): only 2 elites in the pool; Fomorian
    (50% win, SW=1) still pulls 25% of elite picks and owns 65
    kills.
  underdark (86%): Drow at SW=7 fills nearly half of standard
    rolls at 100% win / 1.1hp loss -- free-HP filler.

Roster changes:

  manor    Banshee promoted to elite SW=2 (was standard SW=3,
           99.6% win). Soft 4th elite slot dilutes Revenant share
           ~14% -> ~11%. Standards collapse to Shadow+Poltergeist
           (>=99% win).

  underforge  Helmed Horror SW 1 -> 3. Three-way elite pool drops
              Fire Elemental's share from ~44% to ~33%.

  feywild  Green Hag promoted to elite SW=2 (was standard SW=4).
           Adds soft 3rd elite + removes a 16hp/win standard.
           Standards become Redcap+Will-o-Wisp+Quickling.

  underdark  Drow SW 7 -> 5 (light trim per the user's "lift
             trailers, don't nerf leaders" stance). Standards
             shift toward Hook Horror / Drow Mage.

Phase 1 matrix after Phase 5-C (200 trials, Fighter @ centerline):

  T1  88.5%  spread  1.0   (in band 70-90)
  T2  74.5%  spread 15.0   (in band 62-82)
  T3  56.7%  spread  0.5   (in band 55-75)  +13.5pp
  T4  77.0%  spread 13.0   (over band 45-65, matches 5-B target;
                            spread halved from 25.5)
  T5  58.0%  spread 40.0   (abyss_portal 38% is the residual)

T3 mean lifted +13.5pp; both zones inside band with 0.5pp residual
spread. T4 spread halved (25.5 -> 13.0pp) by lifting feywild
+11.5pp and trimming underdark -4.5pp. T1/T2/T5 untouched.

No test debt -- no production tests pin SpawnWeight or IsElite on
the changed entries (TestMonsterKillTags_GatesKnownMonsters checks
vampire_spawn tags only, unaffected). -short suite green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

gogobee_expedition_difficulty.md

@@ -553,6 +553,90 @@ hump and is fine for "some death" tier shape. Remaining work
 (Phase 5-C+) is T3 roster polish + feywild T4-spread fix — separate
 session.
 
+#### Phase 5-C — T3 polish + T4 spread fix (rosters only)
+
+Phase 5-B's exit named two follow-ups: T3 below band (manor 39 /
+underforge 47 vs 55-75), and the T4 spread (feywild 59 vs underdark
+88 = 30pp asymmetry). Phase 5-C re-runs the Phase 4-A trace on the
+four affected zones at the shipped Phase 5-B cell
+(`TestExpeditionBalance_Phase5C_OutlierDiagnostic`) and identifies
+which monsters own the lethality budget per zone, then applies the
+Phase 4-B toolset (IsElite toggle + SpawnWeight rebalance only — no
+bestiary stat-block touches).
+
+Per-zone reads from the diagnostic (200 trials, L9/L13 Fighter,
+e=23 d=1 burn=50):
+
+  manor_blackspire (53% comp): standards all ≥99% win. Elite pool
+    is the lethality source — Vampire Spawn (72% win, 42 kills) and
+    Revenant (16% win, 31 kills at SW=1) split the kill budget.
+    Revenant can't drop below SW=1, and trimming Vampire Spawn
+    (first attempt: SW 3 → 2) backfired by shifting elite share onto
+    Revenant — kills jumped to 48 and completion fell to 44.5%.
+
+  underforge (49.5% comp): Fire Elemental (57 kills, 61hp/win) +
+    Salamander (33 kills) own elite share. Helmed Horror was the
+    only 100%-win elite but sat at SW=1, providing almost no
+    dilution.
+
+  feywild_crossing (54% comp): Fomorian alone (65 kills, 50% win,
+    SW=1) owns the elite kill budget — only 2 elites in the pool
+    (Night Hag SW=3 + Fomorian SW=1), so Fomorian still gets 25% of
+    elite picks despite the low weight.
+
+  underdark (86% comp): Drow at SW=7 (1801/4164 standard rolls,
+    100% win / 1.1hp loss) is a free-HP filler dominating the
+    standard pool.
+
+Roster changes shipped (`dnd_zone.go`):
+
+  manor_blackspire — Banshee promoted to elite at SW=2 (was SW=3
+    standard, 99.6% win, 11hp loss): adds a soft 4th elite slot,
+    dropping Revenant's elite share ~14% → 11% without changing
+    its presence. Standard floor collapses to Shadow + Poltergeist,
+    both ≥99% win at ≤5hp loss.
+
+  underforge — Helmed Horror SW 1 → 3 (98%+ win, 15hp loss): three
+    roughly-equal elite slots (Salamander 3 + Fire Elemental 3 +
+    Helmed Horror 3), reducing Fire Elemental's elite share from
+    ~44% to ~33%.
+
+  feywild_crossing — Green Hag promoted to elite at SW=2 (was SW=4
+    standard, 98% win, 16hp loss): adds a softer 3rd elite slot,
+    diluting Fomorian's share, AND pulls a moderate-attrition fight
+    out of the standard pool. Standard floor becomes Redcap +
+    Will-o-Wisp + Quickling (all ≥99% win, ≤11hp loss).
+
+  underdark (light trim per user's "lift trailers, don't nerf
+    leaders" stance) — Drow SW 7 → 5: standards shift toward Hook
+    Horror (17.8hp/win) and Drow Mage (16.4hp/win), still safe but
+    with real attrition.
+
+Phase 1 matrix after Phase 5-C (200 trials, Fighter @ centerline):
+
+```
+T1  88.5%  spread  1.0   (crypt 89, goblin 88)            ⬆ band 70-90 — IN BAND
+T2  74.5%  spread 15.0   (forest 82, sunken 67)           ⬆ band 62-82 — IN BAND
+T3  56.7%  spread  0.5   (manor 57, underforge 56.5)      ⬆ band 55-75 — IN BAND  ⬆ +13.5pp
+T4  77.0%  spread 13.0   (feywild 70.5, underdark 83.5)   ⬆ band 45-65 — OVER (matches 5-B target)
+T5  58.0%  spread 40.0   (abyss 38, dragons 78)           ⬆ band 35-55 — borderline (abyss the residual)
+```
+
+T3 mean lifted +13.5pp; both zones land inside the band with a
+0.5pp residual spread. T4 spread halved (25.5 → 13.0pp) by lifting
+feywild +11.5pp and trimming underdark -4.5pp, matching the user's
+chosen "lift mostly, trim lightly" direction. T1/T2/T5 untouched.
+
+**Test debt:** none — no production tests pinned the changed
+SpawnWeight or IsElite values. `TestMonsterKillTags_GatesKnownMonsters`
+checks `vampire_spawn` tags but is unaffected by weight.
+
+**Exit:** T1-T4 all in or above band; T5's abyss_portal (38%) is
+the only remaining sub-band cell and is a tier-asymmetry residual,
+not a per-zone outlier. Phase 5-D could revisit abyss specifically,
+but it's optional — the user's "breezy with some death" target is
+hit across the live tier ladder.
+
 ### Phase 6 — optional MAD / second-order
 
 If post-Phase-3 the bands hold but feel wrong subjectively

internal/plugin/dnd_zone.go

@@ -433,9 +433,23 @@ func zoneManorBlackspire() ZoneDefinition {
 			// becomes a 3-elite pool with balanced dilution, leaving
 			// Shadow/Poltergeist/Banshee as a clean standard floor
 			// (all ≥92% win in the trace).
+			//
+			// Phase 5-C: under shipped HP×1.5/+3 floor, manor still
+			// trailed at 53% (band 55-75). Trace named both Vampire
+			// Spawn (72% win, 42 kills) and Revenant (16% win, 31
+			// kills) as elite-pool killers — Revenant the worse per
+			// appearance, but at SW=1 already. A first attempt
+			// trimmed Vampire Spawn SW 3 → 2; that backfired by
+			// shifting elite share onto Revenant (kills jumped to
+			// 48). Final move: keep the killers' weights, dilute
+			// the elite pool by promoting Banshee (99.6% win as
+			// standard, 11hp loss) to elite at SW=2 — drops
+			// Revenant's elite share ~14% → 11% without removing
+			// it from rotation. Standard floor collapses to
+			// Shadow + Poltergeist (both ≥99% win, ≤5hp loss).
 			{BestiaryID: "shadow", SpawnWeight: 6},
 			{BestiaryID: "poltergeist", SpawnWeight: 5},
-			{BestiaryID: "banshee", SpawnWeight: 3},
+			{BestiaryID: "banshee", SpawnWeight: 2, IsElite: true},
 			{BestiaryID: "wraith", SpawnWeight: 3, IsElite: true},
 			{BestiaryID: "vampire_spawn", SpawnWeight: 3, IsElite: true},
 			{BestiaryID: "revenant", SpawnWeight: 1, IsElite: true},
@@ -480,12 +494,21 @@ func zoneUnderforge() ZoneDefinition {
 		MinRooms:   7,
 		MaxRooms:   9,
 		Enemies: []ZoneEnemy{
+			// Phase 5-C: underforge trailed at 49.5% (band 55-75)
+			// under the shipped HP×1.5/+3 floor. Trace named Fire
+			// Elemental (57 kills, 61hp loss/win) as the dominant
+			// elite killer with Salamander (33 kills) second.
+			// Helmed Horror was the only 100%-win elite but sat at
+			// SW=1, contributing almost no dilution. Lifted Helmed
+			// Horror SW 1 → 3 so the elite pool runs three roughly-
+			// equal slots and Fire Elemental's share drops from
+			// ~44% to ~33% of elite picks.
 			{BestiaryID: "magmin", SpawnWeight: 6},
 			{BestiaryID: "azer", SpawnWeight: 5},
 			{BestiaryID: "flameskull", SpawnWeight: 4},
 			{BestiaryID: "salamander", SpawnWeight: 3, IsElite: true},
 			{BestiaryID: "fire_elemental", SpawnWeight: 3, IsElite: true},
-			{BestiaryID: "helmed_horror", SpawnWeight: 1, IsElite: true},
+			{BestiaryID: "helmed_horror", SpawnWeight: 3, IsElite: true},
 		},
 		Boss: ZoneBoss{
 			BestiaryID:  "boss_emberlord_thyrak",
@@ -528,7 +551,17 @@ func zoneUnderdark() ZoneDefinition {
 		MinRooms:   8,
 		MaxRooms:   10,
 		Enemies: []ZoneEnemy{
-			{BestiaryID: "drow", SpawnWeight: 7},
+			// Phase 5-C: underdark ran 88% (band 45-65, way over)
+			// at the T4 centerline — its sibling feywild sat at
+			// 54%, a 30pp asymmetry. Per [[feedback_difficulty_target]]
+			// the bulk of Phase 5-C lifts feywild rather than nerfing
+			// the leader; this is the "light underdark trim" piece.
+			// Drow at SW=7 owned nearly half of all standard rolls
+			// (1801/4164) at 100% win / 1.1hp loss — a free-HP
+			// filler. Trimmed SW 7 → 5 so the standard pool shifts
+			// toward Hook Horror (17.8hp/win) and Drow Mage
+			// (16.4hp/win) — still safe but with real attrition.
+			{BestiaryID: "drow", SpawnWeight: 5},
 			{BestiaryID: "drow_elite_warrior", SpawnWeight: 4, IsElite: true},
 			{BestiaryID: "drow_mage", SpawnWeight: 3},
 			{BestiaryID: "mind_flayer", SpawnWeight: 2},
@@ -575,10 +608,22 @@ func zoneFeywildCrossing() ZoneDefinition {
 		MinRooms:   8,
 		MaxRooms:   10,
 		Enemies: []ZoneEnemy{
+			// Phase 5-C: feywild trailed at 54% (band 45-65, but
+			// the design goal was to close the 30pp gap with its
+			// underdark sibling at 88%). Trace named Fomorian as
+			// the dominant killer (65 kills, 50% win, SW=1) — a
+			// 2-elite pool with Night Hag at SW=3 meant Fomorian
+			// owned ~25% of elite picks despite its low weight,
+			// and that bracket is where the deaths came from.
+			// Promoted Green Hag to elite (SW=2): adds a softer
+			// 98%-win elite slot to dilute Fomorian's share, and
+			// pulls a 16hp/win standard out of the standard pool
+			// so the standard floor collapses to Redcap + Will-o-
+			// Wisp + Quickling — all ≥99% win, ≤11hp loss.
 			{BestiaryID: "redcap", SpawnWeight: 6},
 			{BestiaryID: "will_o_wisp", SpawnWeight: 5},
 			{BestiaryID: "quickling", SpawnWeight: 5},
-			{BestiaryID: "green_hag", SpawnWeight: 4},
+			{BestiaryID: "green_hag", SpawnWeight: 2, IsElite: true},
 			{BestiaryID: "night_hag", SpawnWeight: 3, IsElite: true},
 			{BestiaryID: "fomorian", SpawnWeight: 1, IsElite: true},
 		},

internal/plugin/expedition_balance_test.go

@@ -1417,6 +1417,204 @@ func zoneSeedSalt(id ZoneID) uint64 {
 	return s
 }
 
+// TestExpeditionBalance_Phase5C_OutlierDiagnostic is the per-zone
+// trace pass for Phase 5-C — the second roster-polish round. Phase
+// 5-B's shipped baseline (HP×1.5, +3 player floor, e=23, d=1, burn=50)
+// landed T1/T2/T4/T5 at or above band, but left T3 at 43% mean
+// (manor 39 / underforge 47 vs band 55-75) and produced a 30pp
+// T4 spread (feywild 59 vs underdark 88) with feywild trailing.
+//
+// This test re-runs the Phase 4-A trace on the four affected zones
+// (manor + underforge as both-trail, feywild as lift-target, underdark
+// as healthy reference / candidate for one mild elite demotion). Same
+// monster-attribution, day-of-end, and elite/std-mix aggregates as
+// Phase 4-A; the difference is the candidate zone set and that all
+// four are reported side-by-side rather than as outlier+sibling pairs.
+//
+// Constraint per the plan doc and Phase 4-B's commit: do not touch
+// monster stat blocks. Tools allowed are IsElite toggle, SpawnWeight
+// rebalance, and zone-scoped boss tuning.
+//
+// Diagnostic-only — no gates. -short skips.
+func TestExpeditionBalance_Phase5C_OutlierDiagnostic(t *testing.T) {
+	if testing.Short() {
+		t.Skip("phase 5-C diagnostic walks 4 zones × 200 trials; -short skips it")
+	}
+
+	const trialsPerZone = 200
+	const baseSeed uint64 = 0xF50C5D
+	// Phase 5-B shipped cell. HP×1.5 and the +3 combat floor are
+	// already wired into the harness via the live constants
+	// (phase5BHPMult, applyPhase5BPlayerFloor); only the three
+	// expedition-side overrides need restating.
+	const eliteThreshold = 23
+	const driftBase = 1
+	const supplyBurnPct = 50
+
+	zones := []struct {
+		id   ZoneID
+		tier ZoneTier
+		role string
+	}{
+		{ZoneManorBlackspire, ZoneTierJourneyman, "TRAIL-T3"},
+		{ZoneUnderforge, ZoneTierJourneyman, "TRAIL-T3"},
+		{ZoneFeywildCrossing, ZoneTierVeteran, "TRAIL-T4"},
+		{ZoneUnderdark, ZoneTierVeteran, "HEALTHY-T4"},
+	}
+
+	type monsterStat struct {
+		appearances    int
+		standardCount  int
+		eliteCount     int
+		wins           int
+		hpLossOnWin    int
+		killAttributed int
+	}
+	type zoneAgg struct {
+		profile     expeditionBalanceProfile
+		completions int
+		deaths      int
+		starves     int
+		monsters    map[string]*monsterStat
+		dayHist     [16]int
+		eliteFights int
+		stdFights   int
+		lastFight   harnessFightTrace
+	}
+
+	report := func(label string, agg *zoneAgg) {
+		total := trialsPerZone
+		compPct := float64(agg.completions) / float64(total) * 100
+		deathPct := float64(agg.deaths) / float64(total) * 100
+		starvePct := float64(agg.starves) / float64(total) * 100
+		t.Logf("─── %-11s %-18s L%-2d  comp=%5.1f%%  death=%5.1f%%  starve=%5.1f%%  elite_fights=%d std_fights=%d ───",
+			label, agg.profile.ZoneID,
+			agg.profile.Level,
+			compPct, deathPct, starvePct,
+			agg.eliteFights, agg.stdFights)
+		names := make([]string, 0, len(agg.monsters))
+		for n := range agg.monsters {
+			names = append(names, n)
+		}
+		sort.Slice(names, func(i, j int) bool {
+			return agg.monsters[names[i]].appearances > agg.monsters[names[j]].appearances
+		})
+		for _, n := range names {
+			m := agg.monsters[n]
+			winPct := 0.0
+			if m.appearances > 0 {
+				winPct = float64(m.wins) / float64(m.appearances) * 100
+			}
+			avgLoss := 0.0
+			if m.wins > 0 {
+				avgLoss = float64(m.hpLossOnWin) / float64(m.wins)
+			}
+			t.Logf("    MON  %-22s appear=%4d (std=%-3d elite=%-3d) win=%5.1f%% avg_hp_loss_on_win=%5.1f kills=%d",
+				n, m.appearances, m.standardCount, m.eliteCount,
+				winPct, avgLoss, m.killAttributed)
+		}
+		bins := make([]string, 0, 14)
+		for d := 1; d <= 14; d++ {
+			if agg.dayHist[d] > 0 {
+				bins = append(bins, fmt.Sprintf("d%d=%d", d, agg.dayHist[d]))
+			}
+		}
+		t.Logf("    END-DAYS  %s", joinZones(bins))
+	}
+
+	for _, z := range zones {
+		level := phase1TierCenterline[z.tier]
+		t.Logf("═══ %-11s %s (L%d Fighter, e=%d d=%d burn=%d, %d trials) ═══",
+			z.role, z.id, level,
+			eliteThreshold, driftBase, supplyBurnPct, trialsPerZone)
+
+		profile := expeditionBalanceProfile{
+			ZoneID:                          z.id,
+			Class:                           ClassFighter,
+			Level:                           level,
+			Supplies:                        makeSupplies(z.tier, SupplyPurchase{StandardPacks: 3}),
+			CampType:                        CampTypeStandard,
+			EliteInterruptThresholdOverride: eliteThreshold,
+			ThreatDriftBaseOverride:         driftBase,
+			SupplyBurnRatePctOverride:       supplyBurnPct,
+		}
+		agg := &zoneAgg{
+			profile:  profile,
+			monsters: map[string]*monsterStat{},
+		}
+
+		for trial := 0; trial < trialsPerZone; trial++ {
+			exp := newHarnessExpedition(profile)
+			char := buildHarnessCharacter(classBalanceProfile{
+				Class: profile.Class,
+				Level: profile.Level,
+			})
+			h := &expeditionHarness{
+				exp:                             exp,
+				char:                            char,
+				rng:                             newHarnessRNG(baseSeed + uint64(trial) + uint64(z.tier)*131 + zoneSeedSalt(z.id)),
+				rollsPerDay:                     harnessHarvestRollsPerDay,
+				eliteInterruptThresholdOverride: eliteThreshold,
+				threatDriftBaseOverride:         driftBase,
+				supplyBurnRatePctOverride:       supplyBurnPct,
+				traceFightStruct: func(ft harnessFightTrace) {
+					m, ok := agg.monsters[ft.MonsterName]
+					if !ok {
+						m = &monsterStat{}
+						agg.monsters[ft.MonsterName] = m
+					}
+					m.appearances++
+					if ft.Elite {
+						m.eliteCount++
+						agg.eliteFights++
+					} else {
+						m.standardCount++
+						agg.stdFights++
+					}
+					if ft.Won {
+						m.wins++
+						loss := ft.HPPre - ft.HPPost
+						if loss < 0 {
+							loss = 0
+						}
+						m.hpLossOnWin += loss
+					}
+					agg.lastFight = ft
+				},
+			}
+			var trialEnd expeditionTrialResult
+			for {
+				res := h.advanceExpeditionOneDay()
+				if res.EndedReason != "" {
+					trialEnd = res
+					break
+				}
+			}
+			switch {
+			case trialEnd.Completed:
+				agg.completions++
+			case trialEnd.Died:
+				agg.deaths++
+				if m, ok := agg.monsters[agg.lastFight.MonsterName]; ok && !agg.lastFight.Won {
+					m.killAttributed++
+				}
+			case trialEnd.StarvedOut:
+				agg.starves++
+			}
+			d := trialEnd.DaysElapsed
+			if d < 1 {
+				d = 1
+			}
+			if d > 14 {
+				d = 14
+			}
+			agg.dayHist[d]++
+		}
+
+		report(z.role, agg)
+	}
+}
+
 // joinZones is a tiny helper kept local to the test file so the
 // per-tier log line reads in one logical chunk without pulling in
 // strings.Join's import for production code.