N5/D2: NPC arcs — Misty stages, Robbie's gift, Thom's final letter

Three flavor arcs on existing per-player counters (no schema, golden
byte-identical):

- Misty: 3 deepening dialogue beats at MistyEncounterCount 5/15/30,
  prepended to the encounter opening the one time the counter lands on a
  threshold. Fiction only — no copy ties a donation to the hidden arena
  effects.
- Robbie: every 10th visit he leaves a consumable "for the trouble,"
  drawn from the dungeon pool at a level-matched tier.
- Thom: paying off the Tier-4 mortgage (no next tier) sends a final
  letter instead of the stock payoff line, plus an inert pet-treat
  keepsake if the player keeps a pet.

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

internal/plugin/adventure_flavor_npcs.go

@@ -24,6 +24,31 @@ var mistyAcceptLines = []string{
 
 const mistyDeclineLine = "She nods once and walks away. She doesn't look back."
 
+// ── Misty — Arc Beats (D2) ─────────────────────────────────────────────────
+//
+// Three deepening dialogue beats keyed to MistyEncounterCount (5 / 15 / 30),
+// prepended to the encounter opening the one time the counter lands on a
+// threshold. Fiction only: nothing here connects a donation to a combat
+// outcome — the arena effects are a hidden discovery mechanic and stay hidden.
+var mistyArcBeats = map[int]string{
+	5: "It's you again. I was hoping it would be. I know your face now -- you're one of the few who ever stops. " +
+		"Most people look right through me. You never have.",
+
+	15: "Can I tell you something? I wasn't always out here asking strangers on the road. " +
+		"I had a home once. A garden that got away from me every summer. Someone who used to wait up. " +
+		"It's gone now, all of it. But you keep reminding me there are still kind people in the world. That's not nothing.",
+
+	30: "I don't think of you as a stranger anymore. Is it strange to say that? " +
+		"I catch myself watching the road for you now -- not for the gold, though I won't pretend it doesn't help. " +
+		"Just to see you're still standing. Whatever's out there, I hope it knows better than to take you from me too.",
+}
+
+// mistyArcBeat returns the deepening dialogue for the exact encounter count at
+// which a Misty stage lands, or "" for every other encounter.
+func mistyArcBeat(encounterCount int) string {
+	return mistyArcBeats[encounterCount]
+}
+
 // ── Arina — Opening Lines ──────────────────────────────────────────────────
 
 var arinaOpenings = []string{

internal/plugin/adventure_flavor_robbie.go

@@ -40,6 +40,11 @@ var robbieMasterworkAlreadyHas = "Oh. I see you already have one of these. Excel
 var robbieAllShopGear = "Nothing fancy today but that's alright. Clean inventory is its own reward. " +
 	"Well. The €%d is the reward. The clean inventory is a bonus. Cheerio!"
 
+// robbieLeftConsumable is appended when Robbie leaves a little something on his
+// every-10th-visit (D2). Takes the item name.
+var robbieLeftConsumable = "Oh -- one more thing. I tucked a %s into your bag on the way out. " +
+	"You've had me round enough times now that it felt rude not to. For the trouble, eh? _winks_"
+
 // ── Room Announcements ───────────────────────────────────────────────────────
 
 var robbieRoomStandard = "🎩 Robbie paid %s a visit and collected %d item(s) from their inventory. " +

internal/plugin/adventure_housing.go

@@ -146,6 +146,18 @@ var thomFreezePet = "Ten missed payments. I've stopped trying for now. The house
 var thomPaidOffNoPet = "Paid off. Noted. The next tier is available when you're ready. I'll be here."
 var thomPaidOffPet = "Paid off. Good. Come in when you're ready for the next tier. I've been thinking about what %s would need in a better space. I have thoughts."
 
+// thomPetTreatItem is the keepsake Thom leaves for the pet on the final
+// mortgage payoff. Inert (Type "card" like the medical-debt card): not a
+// consumable, not gear, and Robbie's sweep skips it.
+func thomPetTreatItem() AdvItem {
+	return AdvItem{
+		Name:  "Krooke's Finest Pet Treat",
+		Type:  "card",
+		Tier:  0,
+		Value: 0,
+	}
+}
+
 // thomGreeting returns an appropriate greeting based on pet state.
 func thomGreeting(char *AdventureCharacter) string {
 	if char.HasPet() && char.PetLevel >= 10 {
@@ -553,11 +565,22 @@ func (p *AdventurePlugin) processMortgagePayments() {
 				freshChar.HouseLoanBalance = 0
 				freshChar.HouseMissedPayments = 0
 				_ = saveAdvCharacter(freshChar)
+				// The last house: no next tier means Thom is done with this
+				// player. A letter, and a treat in the bag if they keep a pet.
+				finalPayoff := houseNextTier(freshChar.HouseTier) == nil
+				if finalPayoff && freshChar.HasPet() {
+					_ = addAdvInventoryItem(freshChar.UserID, thomPetTreatItem())
+				}
 				userMu.Unlock()
-				// Paid off!
-				if freshChar.HasPet() {
+				switch {
+				case finalPayoff && freshChar.HasPet():
+					letter := strings.ReplaceAll(thomFinalLetterPet, "{pet}", freshChar.PetName)
+					_ = p.SendDM(freshChar.UserID, "🏠 "+letter)
+				case finalPayoff:
+					_ = p.SendDM(freshChar.UserID, "🏠 "+thomFinalLetterNoPet)
+				case freshChar.HasPet():
 					_ = p.SendDM(freshChar.UserID, fmt.Sprintf("🏠 %s", fmt.Sprintf(thomPaidOffPet, freshChar.PetName)))
-				} else {
+				default:
 					_ = p.SendDM(freshChar.UserID, fmt.Sprintf("🏠 %s", thomPaidOffNoPet))
 				}
 				continue

internal/plugin/adventure_npc_arcs_test.go

@@ -0,0 +1,91 @@
+package plugin
+
+import (
+	"strings"
+	"testing"
+)
+
+// D2 NPC arcs — pure-helper coverage. None of these touch combat, so the
+// characterization golden is unaffected; these just pin the arc thresholds,
+// gift tiers, and the keepsake shape.
+
+func TestMistyArcBeat_FiresOnlyAtThresholds(t *testing.T) {
+	want := map[int]bool{5: true, 15: true, 30: true}
+	for count := 0; count <= 40; count++ {
+		got := mistyArcBeat(count)
+		if want[count] {
+			if got == "" {
+				t.Errorf("encounter %d: expected an arc beat, got none", count)
+			}
+		} else if got != "" {
+			t.Errorf("encounter %d: expected no arc beat, got %q", count, got)
+		}
+	}
+}
+
+func TestMistyArcBeats_DoNotLeakBuffMechanics(t *testing.T) {
+	// The arena effects are a hidden discovery mechanic; arc copy must never
+	// tie a donation to a combat outcome.
+	banned := []string{"arena", "damage", "buff", "combat", "attack", "heal", "bonus"}
+	for count, beat := range mistyArcBeats {
+		lower := strings.ToLower(beat)
+		for _, b := range banned {
+			if strings.Contains(lower, b) {
+				t.Errorf("beat %d leaks mechanic word %q: %s", count, b, beat)
+			}
+		}
+	}
+}
+
+func TestRobbieGiftTier_MatchesArenaBands(t *testing.T) {
+	cases := []struct {
+		level int
+		tier  int
+	}{
+		{1, 1}, {3, 1}, {4, 2}, {7, 2}, {8, 3}, {12, 3},
+		{13, 4}, {17, 4}, {18, 5}, {20, 5},
+	}
+	for _, c := range cases {
+		if got := robbieGiftTier(c.level); got != c.tier {
+			t.Errorf("robbieGiftTier(%d) = %d, want %d", c.level, got, c.tier)
+		}
+	}
+}
+
+func TestRobbieGiftCadence(t *testing.T) {
+	// The gift lands on every 10th visit and no other.
+	for visit := 1; visit <= 35; visit++ {
+		gives := visit%robbieGiftEveryNVisits == 0
+		if gives != (visit == 10 || visit == 20 || visit == 30) {
+			t.Errorf("visit %d: unexpected gift cadence", visit)
+		}
+	}
+}
+
+func TestThomPetTreat_IsRobbieSafeKeepsake(t *testing.T) {
+	treat := thomPetTreatItem()
+	if treat.Name == "" {
+		t.Fatal("treat has no name")
+	}
+	// Robbie's sweep skips "card" items, so the keepsake survives him.
+	if treat.Type != "card" {
+		t.Errorf("treat type = %q, want card so Robbie's sweep skips it", treat.Type)
+	}
+	if treat.Value != 0 {
+		t.Errorf("treat value = %d, want 0 (inert keepsake)", treat.Value)
+	}
+	// Confirm the sweep filter actually excludes it.
+	if got := robbieQualifyingItems([]AdvItem{treat}, nil); len(got) != 0 {
+		t.Errorf("Robbie would take the treat: %+v", got)
+	}
+}
+
+func TestThomFinalLetterPet_SubstitutesPetName(t *testing.T) {
+	letter := strings.ReplaceAll(thomFinalLetterPet, "{pet}", "Biscuit")
+	if strings.Contains(letter, "{pet}") {
+		t.Error("unsubstituted {pet} placeholder remains")
+	}
+	if !strings.Contains(letter, "Biscuit") {
+		t.Error("pet name not substituted into the letter")
+	}
+}

internal/plugin/adventure_npcs.go

@@ -141,6 +141,12 @@ func (p *AdventurePlugin) npcFireEncounter(userID id.UserID, npc string) {
 		// Pool union: legacy mistyOpenings + D&D MistyGreeting flavor.
 		mistyPool := dndMistyGreetingPool()
 		opening = mistyPool[rand.IntN(len(mistyPool))]
+		// D2 arc: a deepening beat lands the one time the counter hits a
+		// threshold (5/15/30). MistyEncounterCount only ever increments by one
+		// above, so each beat is delivered exactly once.
+		if beat := mistyArcBeat(char.MistyEncounterCount); beat != "" {
+			opening = beat + "\n\n" + opening
+		}
 		prompt = fmt.Sprintf("👤 A woman approaches you.\n\n_%s_\n\n"+
 			"Reply `yes` to give €%d, or `no` to walk away.", opening, mistyCost)
 	case "arina":

internal/plugin/adventure_robbie.go

@@ -164,16 +164,25 @@ func (p *AdventurePlugin) robbieVisitPlayer(userID id.UserID, displayName string
 		gaveCard = true
 	}
 
-	// Update visit count
+	// Update visit count, and every 10th visit leave a small consumable
+	// "for the trouble" (D2 NPC arc).
+	var leftGift *AdvItem
 	char, err := loadAdvCharacter(userID)
 	if err == nil {
 		char.RobbieVisitCount++
+		if char.RobbieVisitCount%robbieGiftEveryNVisits == 0 {
+			if gifts := consumableCache(robbieGiftTier(char.CombatLevel), 1); len(gifts) > 0 {
+				if err := addAdvInventoryItem(userID, gifts[0]); err == nil {
+					leftGift = &gifts[0]
+				}
+			}
+		}
 		_ = saveAdvCharacter(char)
 		_ = upsertPlayerMetaNPCState(userID, npcStateFromAdvChar(char))
 	}
 
 	// Send DM
-	dm := renderRobbieDM(userID, takenItems, totalPayout, masterworkTaken, gaveCard)
+	dm := renderRobbieDM(userID, takenItems, totalPayout, masterworkTaken, gaveCard, leftGift)
 	if err := p.SendDM(userID, dm); err != nil {
 		slog.Error("adventure: robbie: failed to send DM", "user", userID, "err", err)
 	}
@@ -243,7 +252,27 @@ func robbiePlayerHasCard(userID id.UserID) bool {
 
 // ── DM Rendering ─────────────────────────────────────────────────────────────
 
-func renderRobbieDM(userID id.UserID, items []AdvItem, total int64, mwTaken, gaveCard bool) string {
+// robbieGiftEveryNVisits is how often Robbie leaves a consumable behind.
+const robbieGiftEveryNVisits = 10
+
+// robbieGiftTier maps a player's combat level to a consumable tier, matching
+// the arena tier bands (1–3 / 4–7 / 8–12 / 13–17 / 18+).
+func robbieGiftTier(level int) int {
+	switch {
+	case level >= 18:
+		return 5
+	case level >= 13:
+		return 4
+	case level >= 8:
+		return 3
+	case level >= 4:
+		return 2
+	default:
+		return 1
+	}
+}
+
+func renderRobbieDM(userID id.UserID, items []AdvItem, total int64, mwTaken, gaveCard bool, leftGift *AdvItem) string {
 	var sb strings.Builder
 
 	// Opening
@@ -290,6 +319,12 @@ func renderRobbieDM(userID id.UserID, items []AdvItem, total int64, mwTaken, gav
 	}
 	sb.WriteString("\n\n")
 
+	// Every-10th-visit consumable (D2).
+	if leftGift != nil {
+		sb.WriteString(fmt.Sprintf(robbieLeftConsumable, leftGift.Name))
+		sb.WriteString("\n\n")
+	}
+
 	// Closing
 	closing, _ := advPickFlavor(robbieClosings, userID, "robbie_closing")
 	sb.WriteString(closing)

internal/plugin/thom_krooke_mortgage_flavor.go

@@ -120,6 +120,23 @@ var ThomRateDecreasePet = []string{
 		"You can draw your own conclusions.",
 }
 
+// ── FINAL PAYOFF — THE LAST HOUSE (D2 NPC ARC) ────────────────────────────────
+//
+// Sent once, when the Tier-4 "Established" mortgage hits zero — the last house
+// Thom has to sell. There is no next tier, so this is the last time Thom has
+// business with the player. A letter, and (if they keep a pet) a treat left in
+// the bag. Substitute {pet} with strings.ReplaceAll at the call site.
+
+var thomFinalLetterNoPet = "Paid off. All of it. There is no next tier -- you've bought the last house I had to sell you.\n\n" +
+	"I've closed a great many mortgages. Thirty-one years, Krooke Realty. Most people I stop thinking about the hour the balance hits zero, and I have never once considered that a loss. I am writing to tell you that you appear to be an exception. I have not decided how I feel about that. I am telling you anyway, which should indicate something.\n\n" +
+	"The door is yours, the roof is yours, the ground it stands on is yours. Nobody sends you a bill for it ever again. Walk through it whenever you like.\n\n" +
+	"-- Thom Krooke, Krooke Realty"
+
+var thomFinalLetterPet = "Paid off. All of it. There is no next tier -- you own it outright now, walls and roof and the ground it sits on.\n\n" +
+	"I've enclosed something for {pet}. A treat. The good kind -- not the sort they sell by the sack, I had it sent from a place I trust. Give it to {pet} tonight and don't you dare ration it, and don't 'save it for a special occasion' either. Tonight IS the occasion. {pet} has spent this entire mortgage living in a house that wasn't finished being paid for, and now it is, and {pet} should know the difference even if {pet} can't be told in words.\n\n" +
+	"You did a fine thing, getting {pet} a home that is truly yours. I won't say it a second time.\n\n" +
+	"-- Thom Krooke, Krooke Realty"
+
 // ── NO CHANGE (NEVER SENT) ────────────────────────────────────────────────────
 // Thom does not send neutral news.
 // If rate is unchanged week over week: no DM. No notification. Nothing.