N5/D4: secret content pass — treasure-cache secret rooms + cross-zone keys

Secret rooms were dead content: every NodeKindSecret node silently
collapsed to a normal exploration fight and its authored LootBias
(1.5-3.0) was never read at runtime. D4 makes them what they read as —
no-combat treasure caches.

resolveRoom now diverts a secret node (keyed off the graph node, since
CurrentRoomType has already lost the kind) to resolveSecretRoom before
the RoomType switch — shared by manual !zone advance, !expedition run
autopilot, and the sim. Each secret pays a guaranteed journal page
(the D1a grant hook built "for secret rooms"), a LootBias-weighted
treasure roll (floored at elite weight), and a guaranteed zone-tier
consumable cache, with bespoke in-world discovery flavor.

Underdark was the only T2+ zone with no secret; added at throne_gallery
on the universal R4 tail (Lost Reliquary, Perception DC 17), merging to
throne_steps so it's length-neutral.

Two cross-zone keys: the Sunken Temple's Coral Reliquary grants a Sunken
Sigil that opens a Sealed Reliquary in Manor Blackspire; the Underforge's
Forge Vault grants an Underforge Seal that opens a Sealed Vault in the
Underdark. Keys are persistent inventory items matched against LockKey
key_id; grants are idempotent.

Graph validator + no-soft-lock pass on both touched graphs; combat golden
byte-identical; go build/vet/test green repo-wide.

Claude-Session: https://claude.ai/code/session_017mEwUmmS7aQTP2NQXj6rUa

internal/plugin/adventure_flavor_campaign.go

@@ -149,6 +149,103 @@ func (p *AdventurePlugin) grantJournalPage(userID id.UserID, rng *rand.Rand) str
 		journalPages[page-1].Title, page, journalTotalPages)
 }
 
+// --- N5/D4 secret content pass ---------------------------------------------
+//
+// Every NodeKindSecret room resolves as a no-combat treasure cache (see
+// resolveSecretRoom in dnd_zone_combat.go). Finding it — via the perception /
+// stat check on the fork, or a cross-zone key — is the reward: a guaranteed
+// journal page, a LootBias-weighted treasure roll, and a guaranteed consumable
+// cache. The flavor and the key catalog live here with the rest of the
+// campaign; the resolution mechanics live next to the other room resolvers.
+
+// secretRoomCacheCount is how many zone-tier consumables a secret room always
+// hands over, so the room pays out something visible even for a player who has
+// every page and misses the treasure roll.
+const secretRoomCacheCount = 2
+
+// crossZoneKey pairs a source secret room with the key item it grants. The key
+// is a plain inventory item; a LockKey edge in the destination zone matches its
+// lower-cased Name against lock_data.key_id (see evaluateEdgeLock). Keys persist
+// in inventory, so the unlock is permanent once earned.
+type crossZoneKey struct {
+	item       AdvItem
+	unlocksIn  ZoneID // destination zone, for the grant narration
+	unlockHint string // what the key opens, surfaced when it's granted
+}
+
+// secretRoomKeys — the two cross-zone keys (N5/D4). A Sunken Temple sigil opens
+// a sealed reliquary in Manor Blackspire; an Underforge seal opens a vault deep
+// in the Underdark throne approach. Keyed by the source secret's node ID.
+var secretRoomKeys = map[string]crossZoneKey{
+	"sunken_temple.coral_reliquary": {
+		item:       AdvItem{Name: "Sunken Sigil", Type: "key", Tier: 2},
+		unlocksIn:  ZoneManorBlackspire,
+		unlockHint: "a drowned god's mark — Blackspire has a door that remembers it",
+	},
+	"underforge.forge_vault": {
+		item:       AdvItem{Name: "Underforge Seal", Type: "key", Tier: 3},
+		unlocksIn:  ZoneUnderdark,
+		unlockHint: "the forge's own brand — something in the deep roads was promised its work",
+	},
+}
+
+// grantSecretRoomKey hands over the cross-zone key a secret room carries, if it
+// carries one and the player isn't already holding it. Idempotent: re-finding
+// the room on a later run won't stack duplicate keys. Returns the narration line
+// (empty when the room grants no key, the player already has it, or on error).
+func (p *AdventurePlugin) grantSecretRoomKey(userID id.UserID, node ZoneNode) string {
+	key, ok := secretRoomKeys[node.NodeID]
+	if !ok {
+		return ""
+	}
+	items, err := loadAdvInventory(userID)
+	if err != nil {
+		return ""
+	}
+	want := strings.ToLower(key.item.Name)
+	for _, it := range items {
+		if strings.ToLower(it.Name) == want {
+			return "" // already earned — don't stack it
+		}
+	}
+	if err := addAdvInventoryItem(userID, key.item); err != nil {
+		slog.Error("secret room: grant key", "user", userID, "key", key.item.Name, "err", err)
+		return ""
+	}
+	return fmt.Sprintf("🗝 **%s** — %s.", key.item.Name, key.unlockHint)
+}
+
+// secretRoomDiscovery is the bespoke in-world discovery line for a secret room,
+// keyed by node ID. Not TwinBee's voice — the same in-world register the journal
+// pages use. Nodes without an entry fall back to a generic line built from the
+// node label.
+var secretRoomDiscovery = map[string]string{
+	"crypt_valdris.secret_chamber":      "🔍 **A sealed chamber.** The other grave-robbers pried at the wrong wall. This one gives — Valdris kept something back even from his own tomb.",
+	"forest_shadows.sapling_shrine":     "🔍 **The Sapling Shrine.** A ring of young antlers grown from the dirt, and something votive left at the centre — an offering the King's shell never came back to claim.",
+	"sunken_temple.coral_reliquary":     "🔍 **The Coral Reliquary.** Behind a lattice of living coral, a niche the flood sealed rather than drowned. What the temple hid, it hid well.",
+	"manor_blackspire.hidden_oratory":   "🔍 **The Hidden Oratory.** A chapel with no door in the floor plan, kept for a tenant the deeds refuse to name.",
+	"manor_blackspire.sealed_reliquary": "🔍 **The Sealed Reliquary.** The drowned god's sigil bites into the lock and turns. Blackspire kept a piece of the temple's secret behind a door only the temple could open.",
+	"underforge.forge_vault":            "🔍 **The Forge Vault.** A strongroom off the unbanked heat, its ledger of commissions all addressed elsewhere and long overdue.",
+	"underdark.lost_reliquary":          "🔍 **A lost reliquary.** A shrine the deep roads swallowed whole, still lit, still waiting on a procession that stopped coming a long age ago.",
+	"underdark.sealed_forge_vault":      "🔍 **The Sealed Vault.** The Underforge's brand fits the seam, and the deep-road door gives up what the forge sent ahead — payment on the old account.",
+	"feywild_crossing.illusion_garden":  "🔍 **The Illusion Garden.** A too-kind grove that isn't there when you look straight at it. He can afford beauty here; it costs him nothing to keep.",
+	"dragons_lair.hoard_pillar":         "🔍 **A pillar of hoard.** Coin drifted to the ceiling around a single column the wyrm guards more than gold — as if something at its heart were worth more.",
+	"abyss_portal.reality_seam":         "🔍 **A seam in the real.** The gate's arithmetic frays here, and through the frayed place a hand once reached to leave a thing behind on the way out.",
+}
+
+// secretRoomDiscoveryLine returns the discovery flavor for a secret room,
+// falling back to a label-driven generic when the node has no bespoke entry.
+func secretRoomDiscoveryLine(node ZoneNode) string {
+	if line, ok := secretRoomDiscovery[node.NodeID]; ok {
+		return line
+	}
+	label := node.Label
+	if label == "" {
+		label = "a hidden room"
+	}
+	return fmt.Sprintf("🔍 **%s** — a room the others walked past. Something was left here for whoever looked closer.", label)
+}
+
 // bossEpilogues ties each zone boss's death to the Hollow King arc: a 2-3
 // sentence capstone appended to the boss-down moment. Forest of Shadows is the
 // King himself — but what falls there is a shell he shed, which is why the arc

internal/plugin/adventure_secret_room_test.go

@@ -0,0 +1,216 @@
+package plugin
+
+import (
+	"strings"
+	"testing"
+
+	"maunium.net/go/mautrix/id"
+)
+
+// registeredSecretNodes collects every NodeKindSecret node across all
+// registered zone graphs, keyed by node ID.
+func registeredSecretNodes(t *testing.T) map[string]ZoneNode {
+	t.Helper()
+	out := map[string]ZoneNode{}
+	for _, z := range allZones() {
+		g, ok := loadZoneGraph(z.ID)
+		if !ok {
+			continue
+		}
+		for id, n := range g.Nodes {
+			if n.Kind == NodeKindSecret {
+				out[id] = n
+			}
+		}
+	}
+	return out
+}
+
+// TestSecretRoomDiscovery_EverySecretHasBespokeFlavor guards that no secret
+// node ships on the generic fallback — every one gets an authored line. Catches
+// a future secret room added without a discovery entry.
+func TestSecretRoomDiscovery_EverySecretHasBespokeFlavor(t *testing.T) {
+	for id, n := range registeredSecretNodes(t) {
+		if _, ok := secretRoomDiscovery[id]; !ok {
+			t.Errorf("secret node %q (%q) has no bespoke discovery line", id, n.Label)
+		}
+		if line := secretRoomDiscoveryLine(n); strings.TrimSpace(line) == "" {
+			t.Errorf("secret node %q produced an empty discovery line", id)
+		}
+	}
+}
+
+func TestSecretRoomDiscoveryLine_FallsBackOnUnknownNode(t *testing.T) {
+	n := ZoneNode{NodeID: "made_up.node", Kind: NodeKindSecret, Label: "Nowhere Nook"}
+	line := secretRoomDiscoveryLine(n)
+	if !strings.Contains(line, "Nowhere Nook") {
+		t.Errorf("fallback should name the node label, got: %s", line)
+	}
+}
+
+// TestSecretRoomKeys_UnlockRealDestinationEdges is the cross-zone-key
+// consistency check: every key's item Name must match a LockKey edge's key_id
+// (lower-cased) in its destination zone, and every source must be a real secret
+// room. A typo between the granted item name and the authored key_id would
+// silently make a vault permanently unreachable; this catches it.
+func TestSecretRoomKeys_UnlockRealDestinationEdges(t *testing.T) {
+	secrets := registeredSecretNodes(t)
+	for srcNode, key := range secretRoomKeys {
+		if _, ok := secrets[srcNode]; !ok {
+			t.Errorf("key source %q is not a registered secret room", srcNode)
+		}
+		g, ok := loadZoneGraph(key.unlocksIn)
+		if !ok {
+			t.Errorf("%s: destination zone %q has no graph", srcNode, key.unlocksIn)
+			continue
+		}
+		wantKeyID := strings.ToLower(key.item.Name)
+		found := false
+		for _, outs := range g.Edges {
+			for _, e := range outs {
+				if e.Lock == LockKey && strings.ToLower(lockDataString(e.LockData, "key_id")) == wantKeyID {
+					found = true
+				}
+			}
+		}
+		if !found {
+			t.Errorf("key %q (from %s) has no LockKey edge with key_id=%q in zone %q — vault unreachable",
+				key.item.Name, srcNode, wantKeyID, key.unlocksIn)
+		}
+	}
+}
+
+// TestCrossZoneKey_UnlocksWithItemNotWithout exercises the runtime lock
+// evaluation end-to-end on a real authored edge.
+func TestCrossZoneKey_UnlocksWithItemNotWithout(t *testing.T) {
+	g, ok := loadZoneGraph(ZoneManorBlackspire)
+	if !ok {
+		t.Fatal("manor graph missing")
+	}
+	var keyEdge ZoneEdge
+	for _, e := range g.outgoingEdges("manor_blackspire.upper_hall") {
+		if e.Lock == LockKey {
+			keyEdge = e
+		}
+	}
+	if keyEdge.To == "" {
+		t.Fatal("no LockKey edge off manor upper_hall")
+	}
+
+	base := edgeUnlockCtx{RunID: "r", FromNode: "manor_blackspire.upper_hall"}
+	if ok, _ := evaluateEdgeLock(keyEdge, base); ok {
+		t.Error("edge should be locked without the key in inventory")
+	}
+
+	withKey := base
+	withKey.InventoryNames = map[string]bool{"sunken sigil": true}
+	if ok, reason := evaluateEdgeLock(keyEdge, withKey); !ok {
+		t.Errorf("edge should unlock with the sigil in inventory, got locked: %s", reason)
+	}
+}
+
+// TestGrantSecretRoomKey_GrantsOnceIdempotent verifies a key-bearing secret
+// hands its key over exactly once.
+func TestGrantSecretRoomKey_GrantsOnceIdempotent(t *testing.T) {
+	townTestDB(t)
+	p := &AdventurePlugin{}
+	u := id.UserID("@keyholder:test.invalid")
+
+	node := ZoneNode{NodeID: "sunken_temple.coral_reliquary", Kind: NodeKindSecret}
+	line := p.grantSecretRoomKey(u, node)
+	if !strings.Contains(line, "Sunken Sigil") {
+		t.Fatalf("first grant should name the key, got: %q", line)
+	}
+
+	items, err := loadAdvInventory(u)
+	if err != nil {
+		t.Fatalf("load inventory: %v", err)
+	}
+	sigils := 0
+	for _, it := range items {
+		if strings.EqualFold(it.Name, "Sunken Sigil") {
+			sigils++
+		}
+	}
+	if sigils != 1 {
+		t.Fatalf("want exactly 1 Sunken Sigil, got %d", sigils)
+	}
+
+	// Second find on a later run must not stack a duplicate.
+	if again := p.grantSecretRoomKey(u, node); again != "" {
+		t.Errorf("re-finding the room should not re-grant the key, got: %q", again)
+	}
+	items, _ = loadAdvInventory(u)
+	sigils = 0
+	for _, it := range items {
+		if strings.EqualFold(it.Name, "Sunken Sigil") {
+			sigils++
+		}
+	}
+	if sigils != 1 {
+		t.Fatalf("still want exactly 1 Sunken Sigil after re-find, got %d", sigils)
+	}
+}
+
+// TestGrantSecretRoomKey_NoKeyForPlainSecret confirms a secret room that carries
+// no cross-zone key stays silent.
+func TestGrantSecretRoomKey_NoKeyForPlainSecret(t *testing.T) {
+	townTestDB(t)
+	p := &AdventurePlugin{}
+	u := id.UserID("@plain:test.invalid")
+	node := ZoneNode{NodeID: "forest_shadows.sapling_shrine", Kind: NodeKindSecret}
+	if line := p.grantSecretRoomKey(u, node); line != "" {
+		t.Errorf("plain secret should grant no key, got: %q", line)
+	}
+}
+
+// TestResolveSecretRoom_GrantsPageCacheAndKey checks the full treasure-cache
+// payout: a journal page, the consumable cache, and (for a key-bearing secret)
+// the cross-zone key — with no combat touching HP.
+func TestResolveSecretRoom_GrantsPageCacheAndKey(t *testing.T) {
+	townTestDB(t)
+	p := &AdventurePlugin{}
+	u := id.UserID("@secret:test.invalid")
+
+	zone, ok := getZone(ZoneSunkenTemple)
+	if !ok {
+		t.Fatal("sunken temple zone missing")
+	}
+	node := ZoneNode{
+		NodeID: "sunken_temple.coral_reliquary", Kind: NodeKindSecret,
+		Label:   "Coral Reliquary",
+		Content: ZoneNodeContent{LootBias: 1.8},
+	}
+	run := &DungeonRun{UserID: string(u), ZoneID: ZoneSunkenTemple, CurrentNode: node.NodeID}
+
+	out := p.resolveSecretRoom(u, run, zone, node)
+	if !strings.Contains(out, "Coral Reliquary") {
+		t.Errorf("outcome should carry the discovery line:\n%s", out)
+	}
+
+	// A journal page was granted (fresh player, nothing found yet).
+	if mask, err := loadJournalPages(u); err != nil || journalPageCount(mask) != 1 {
+		t.Fatalf("want exactly 1 journal page granted, got count=%d err=%v", journalPageCount(mask), err)
+	}
+
+	// The guaranteed cache + the cross-zone key are in inventory.
+	items, err := loadAdvInventory(u)
+	if err != nil {
+		t.Fatalf("load inventory: %v", err)
+	}
+	var caches, keys int
+	for _, it := range items {
+		switch {
+		case it.Type == "key":
+			keys++
+		case it.Type == "consumable":
+			caches++
+		}
+	}
+	if caches != secretRoomCacheCount {
+		t.Errorf("want %d cache consumables, got %d", secretRoomCacheCount, caches)
+	}
+	if keys != 1 {
+		t.Errorf("want the Sunken Sigil key granted, got %d keys", keys)
+	}
+}

internal/plugin/dnd_zone_cmd.go

@@ -988,6 +988,25 @@ func (p *AdventurePlugin) streamFlowThen(userID id.UserID, phaseMessages []strin
 // inter-phase delays — see resolveCombatRoom for the contract. For
 // non-combat rooms (entry, trap), phases is nil and outcome carries the
 // resolution narration.
+// currentSecretNode returns the run's current graph node when it is a secret
+// room, so resolveRoom can divert it to the treasure-cache resolver. Returns
+// false for a non-secret node, an unknown zone, or a legacy row that never got
+// a CurrentNode written (those pre-date branching graphs and have no secrets).
+func currentSecretNode(run *DungeonRun) (ZoneNode, bool) {
+	if run.CurrentNode == "" {
+		return ZoneNode{}, false
+	}
+	g, ok := loadZoneGraph(run.ZoneID)
+	if !ok {
+		return ZoneNode{}, false
+	}
+	n, ok := g.Nodes[run.CurrentNode]
+	if !ok || n.Kind != NodeKindSecret {
+		return ZoneNode{}, false
+	}
+	return n, true
+}
+
 func (p *AdventurePlugin) resolveRoom(userID id.UserID, run *DungeonRun, zone ZoneDefinition, compact bool) (intro string, phases []string, outcome string, ended bool, err error) {
 	// Revisit R2 — a cleared room stays cleared. Advancing out of a room the
 	// player backtracked into must not re-roll its combat or re-arm its trap.
@@ -1004,6 +1023,14 @@ func (p *AdventurePlugin) resolveRoom(userID id.UserID, run *DungeonRun, zone Zo
 	if run.RoomIsCleared(run.CurrentRoom) {
 		return
 	}
+	// N5/D4 — a secret room is a no-combat treasure cache, not the exploration
+	// fight its RoomType collapses to. Keyed off the graph node (which still
+	// carries NodeKindSecret) rather than CurrentRoomType (which does not), so
+	// it must be checked before the RoomType switch below.
+	if node, ok := currentSecretNode(run); ok {
+		outcome = p.resolveSecretRoom(userID, run, zone, node)
+		return
+	}
 	switch run.CurrentRoomType() {
 	case RoomEntry:
 		return

internal/plugin/dnd_zone_combat.go

@@ -202,6 +202,52 @@ func scanMoodEventsFromEvents(runID string, events []CombatEvent) (nat20s, nat1s
 //
 // Higher-tier zones currently fall through to the pre-D2a flat-percent
 // nick — D3a/D4a will add Tier 2+ trap catalogs.
+// resolveSecretRoom resolves a NodeKindSecret room as a no-combat treasure
+// cache (N5/D4). Finding the secret — via the perception/stat check on the fork
+// that hangs it, or a cross-zone key — is the reward: a guaranteed journal page
+// (the Hollow King's fragments gather in hidden rooms), a LootBias-weighted
+// treasure roll, a guaranteed zone-tier consumable cache, and, for the two
+// key-bearing secrets, a cross-zone key. No enemy, no threat.
+//
+// LootBias has been authored on every secret node since the branching-zones
+// phase and was dead code until now; it finally scales the treasure weight here.
+func (p *AdventurePlugin) resolveSecretRoom(userID id.UserID, run *DungeonRun, zone ZoneDefinition, node ZoneNode) string {
+	var b strings.Builder
+	b.WriteString(secretRoomDiscoveryLine(node))
+
+	var rewards []string
+	if line := p.grantJournalPage(userID, nil); line != "" {
+		rewards = append(rewards, line)
+	}
+	if line := p.grantSecretRoomKey(userID, node); line != "" {
+		rewards = append(rewards, line)
+	}
+
+	// LootBias-weighted treasure roll. Floors at the elite weight so even the
+	// leanest secret out-rolls a standard kill; the richest (abyss 3.0) still
+	// rolls below a boss. checkTreasureDrop DMs the discovery itself on a hit,
+	// exactly as a combat-room drop does, so it isn't folded into the outcome.
+	weight := node.Content.LootBias
+	if weight < advTreasureWeightElite {
+		weight = advTreasureWeightElite
+	}
+	p.rollZoneTreasure(userID, zone.ID, weight)
+
+	// Guaranteed cache so the room always pays out something visible.
+	for _, item := range consumableCache(int(zone.Tier), secretRoomCacheCount) {
+		it := item
+		if line := p.grantZoneItem(userID, &it, "🧪"); line != "" {
+			rewards = append(rewards, line)
+		}
+	}
+
+	if len(rewards) > 0 {
+		b.WriteString("\n\n")
+		b.WriteString(strings.Join(rewards, "\n"))
+	}
+	return b.String()
+}
+
 func (p *AdventurePlugin) resolveTrapRoom(userID id.UserID, run *DungeonRun, zone ZoneDefinition) (damage int, narration string) {
 	dndChar, _ := LoadDnDCharacter(userID)
 	if dndChar == nil {

internal/plugin/zone_graph_manor_blackspire.go

@@ -34,6 +34,12 @@ package plugin
 // hangs off the open spoke of upper_hall (cheapest gate, hardest fight);
 // the SECRET sits behind the highest-DC Perception with its loot bias
 // preserved.
+//
+// N5/D4 adds a fourth upper_hall spoke: the Sealed Reliquary, a cross-zone
+// key vault (LockKey "sunken sigil", earned in the Sunken Temple's Coral
+// Reliquary). A one-node loot shortcut back to spire_corridor — reachable
+// only by a player who found the sigil, so it never shows on the longest
+// path and the 23-node band is unchanged.
 
 func zoneManorBlackspireGraph() ZoneGraph {
 	nodes := []ZoneNode{
@@ -108,6 +114,12 @@ func zoneManorBlackspireGraph() ZoneGraph {
 		{NodeID: "manor_blackspire.reliquary_dust", Kind: NodeKindExploration,
 			Label: "Reliquary Dust", PosX: 18, PosY: 2},
 
+		// upper_hall — cross-zone key spoke (N5/D4). A Sunken Temple sigil
+		// opens this vault; a loot-rich shortcut back to the spire corridor.
+		{NodeID: "manor_blackspire.sealed_reliquary", Kind: NodeKindSecret,
+			Label: "Sealed Reliquary", PosX: 16, PosY: -2,
+			Content: ZoneNodeContent{LootBias: 2.2}},
+
 		// upper_hall — level-min spoke (tower).
 		{NodeID: "manor_blackspire.tower_observatory", Kind: NodeKindExploration,
 			Label: "Tower Observatory", PosX: 16, PosY: 4},
@@ -174,6 +186,9 @@ func zoneManorBlackspireGraph() ZoneGraph {
 		{From: "manor_blackspire.upper_hall", To: "manor_blackspire.tower_observatory",
 			Lock: LockLevelMin, LockData: map[string]any{"min_level": 7},
 			Hint: "a spiral stair that creaks ominously — climb only if you trust your footing", Weight: 3},
+		{From: "manor_blackspire.upper_hall", To: "manor_blackspire.sealed_reliquary",
+			Lock: LockKey, LockData: map[string]any{"key_id": "sunken sigil"},
+			Hint: "a panel scored with a drowned god's mark — you'd need its twin to open it", Weight: 4},
 
 		// Master Bedroom spoke (elite).
 		{From: "manor_blackspire.master_bedroom", To: "manor_blackspire.grim_balcony", Lock: LockNone},
@@ -185,6 +200,9 @@ func zoneManorBlackspireGraph() ZoneGraph {
 		{From: "manor_blackspire.choir_balcony", To: "manor_blackspire.reliquary_dust", Lock: LockNone},
 		{From: "manor_blackspire.reliquary_dust", To: "manor_blackspire.spire_corridor", Lock: LockNone},
 
+		// Sealed Reliquary spoke (cross-zone key — Sunken Sigil).
+		{From: "manor_blackspire.sealed_reliquary", To: "manor_blackspire.spire_corridor", Lock: LockNone},
+
 		// Tower spoke.
 		{From: "manor_blackspire.tower_observatory", To: "manor_blackspire.spiral_ascent", Lock: LockNone},
 		{From: "manor_blackspire.spiral_ascent", To: "manor_blackspire.telescope_attic", Lock: LockNone},

internal/plugin/zone_graph_manor_blackspire_test.go

@@ -12,22 +12,24 @@ func TestManorBlackspireGraph_Registered(t *testing.T) {
 	}
 	// Long-expedition D1-c widened this zone from 11 → 35 nodes so the
 	// longest entry→boss walk lands in the T3 [22,26] traversal band.
-	if len(g.Nodes) != 35 {
-		t.Errorf("nodes = %d, want 35", len(g.Nodes))
+	// N5/D4 added the Sealed Reliquary cross-zone vault → 36.
+	if len(g.Nodes) != 36 {
+		t.Errorf("nodes = %d, want 36", len(g.Nodes))
 	}
 }
 
-// TestManorBlackspireGraph_TwoStackedThreeWayForks captures the design
-// shape: both great_hall and upper_hall expose three options.
-func TestManorBlackspireGraph_TwoStackedThreeWayForks(t *testing.T) {
+// TestManorBlackspireGraph_StackedForks captures the design shape: great_hall
+// exposes three options; upper_hall exposes four since N5/D4 added the Sealed
+// Reliquary key spoke (the other three remain the elite/secret/tower gates).
+func TestManorBlackspireGraph_StackedForks(t *testing.T) {
 	g := zoneManorBlackspireGraph()
-	for _, hub := range []string{
-		"manor_blackspire.great_hall",
-		"manor_blackspire.upper_hall",
-	} {
-		outs := g.outgoingEdges(hub)
-		if len(outs) != 3 {
-			t.Errorf("%s outgoing = %d, want 3", hub, len(outs))
+	want := map[string]int{
+		"manor_blackspire.great_hall": 3,
+		"manor_blackspire.upper_hall": 4,
+	}
+	for hub, n := range want {
+		if outs := g.outgoingEdges(hub); len(outs) != n {
+			t.Errorf("%s outgoing = %d, want %d", hub, len(outs), n)
 		}
 	}
 }
@@ -43,6 +45,7 @@ func TestManorBlackspireGraph_AllSpokesReachBoss(t *testing.T) {
 		"manor_blackspire.master_bedroom",
 		"manor_blackspire.hidden_oratory",
 		"manor_blackspire.tower_observatory",
+		"manor_blackspire.sealed_reliquary",
 	} {
 		if !reachable(g, leaf, "manor_blackspire.boss") {
 			t.Errorf("%s unreachable to boss", leaf)

internal/plugin/zone_graph_underdark.go

@@ -61,6 +61,15 @@ package plugin
 //     Garrison) and the multi-region transition a teeth-y interrupt.
 // The deep_chasm spur stays anchor-light (harvest, no second trap/elite)
 // so the CON-gated climb keeps its "denser loot, less fighting" identity.
+//
+// N5/D4 turns throne_gallery (R4 tail, which every arm passes through) into
+// a fork with two secret spokes, both merging to throne_steps so either is
+// length-neutral vs the inner-hall path:
+//   - Lost Reliquary — the Underdark's own perception-gated secret (DC 17).
+//   - Sealed Vault — the cross-zone key vault opened by an Underforge Seal
+//     (earned in the Underforge's Forge Vault). LockKey "underforge seal".
+// Placed on the universal R4 tail, not in an arm, so the secrets are
+// reachable no matter which region the walk took.
 
 func zoneUnderdarkGraph() ZoneGraph {
 	r1 := "underdark_surface_tunnels"
@@ -163,10 +172,22 @@ func zoneUnderdarkGraph() ZoneGraph {
 			Label: "Guard Post", PosX: 24, PosY: 2},
 		{NodeID: "underdark.throne_doors", Kind: NodeKindExploration, RegionID: r4,
 			Label: "Riven Doors", PosX: 25, PosY: 2},
-		{NodeID: "underdark.throne_gallery", Kind: NodeKindExploration, RegionID: r4,
+		{NodeID: "underdark.throne_gallery", Kind: NodeKindFork, RegionID: r4,
 			Label: "Throne Gallery", PosX: 26, PosY: 2},
 		{NodeID: "underdark.throne_inner_hall", Kind: NodeKindExploration, RegionID: r4,
 			Label: "Inner Hall", PosX: 27, PosY: 2},
+
+		// N5/D4 secret spokes off the throne gallery (both merge to
+		// throne_steps, so either detour is length-neutral vs the inner-hall
+		// path). lost_reliquary is the Underdark's own perception-gated secret;
+		// sealed_forge_vault is the cross-zone key vault opened by an Underforge
+		// Seal (earned in the Underforge's Forge Vault).
+		{NodeID: "underdark.lost_reliquary", Kind: NodeKindSecret, RegionID: r4,
+			Label: "Lost Reliquary", PosX: 27, PosY: 0,
+			Content: ZoneNodeContent{LootBias: 2.0}},
+		{NodeID: "underdark.sealed_forge_vault", Kind: NodeKindSecret, RegionID: r4,
+			Label: "Sealed Vault", PosX: 27, PosY: 4,
+			Content: ZoneNodeContent{LootBias: 2.2}},
 		{NodeID: "underdark.throne_steps", Kind: NodeKindExploration, RegionID: r4,
 			Label: "Throne Steps", PosX: 28, PosY: 2},
 		{NodeID: "underdark.boss", Kind: NodeKindBoss, IsBoss: true, RegionID: r4,
@@ -232,7 +253,15 @@ func zoneUnderdarkGraph() ZoneGraph {
 		{From: "underdark.throne_antechamber", To: "underdark.throne_guard_post", Lock: LockNone},
 		{From: "underdark.throne_guard_post", To: "underdark.throne_doors", Lock: LockNone},
 		{From: "underdark.throne_doors", To: "underdark.throne_gallery", Lock: LockNone},
-		{From: "underdark.throne_gallery", To: "underdark.throne_inner_hall", Lock: LockNone},
+		{From: "underdark.throne_gallery", To: "underdark.throne_inner_hall", Lock: LockNone, Weight: 1},
+		{From: "underdark.throne_gallery", To: "underdark.lost_reliquary",
+			Lock: LockPerception, LockData: map[string]any{"dc": 17},
+			Hint: "a side-shrine still lit, off the gallery's blind end", Weight: 2},
+		{From: "underdark.throne_gallery", To: "underdark.sealed_forge_vault",
+			Lock: LockKey, LockData: map[string]any{"key_id": "underforge seal"},
+			Hint: "a deep-road door branded by a forge you may have passed", Weight: 3},
+		{From: "underdark.lost_reliquary", To: "underdark.throne_steps", Lock: LockNone},
+		{From: "underdark.sealed_forge_vault", To: "underdark.throne_steps", Lock: LockNone},
 		{From: "underdark.throne_inner_hall", To: "underdark.throne_steps", Lock: LockNone},
 		{From: "underdark.throne_steps", To: "underdark.boss", Lock: LockNone},
 	}

internal/plugin/zone_graph_underdark_test.go

@@ -9,8 +9,10 @@ func TestUnderdarkGraph_Registered(t *testing.T) {
 	}
 	// Long-expedition D1-d widened this zone from 10 → 46 nodes so the
 	// longest entry→boss walk lands in the T4 [28,34] traversal band.
-	if len(g.Nodes) != 46 {
-		t.Errorf("nodes = %d, want 46", len(g.Nodes))
+	// N5/D4 added two throne-gallery secret spokes (Lost Reliquary +
+	// Sealed Vault) → 48.
+	if len(g.Nodes) != 48 {
+		t.Errorf("nodes = %d, want 48", len(g.Nodes))
 	}
 }