diff --git a/lib/src/core/engine/chest_service.dart b/lib/src/core/engine/chest_service.dart
new file mode 100644
index 0000000..2ad2897
--- /dev/null
+++ b/lib/src/core/engine/chest_service.dart
@@ -0,0 +1,274 @@
+import 'package:flutter/foundation.dart';
+
+import 'package:asciineverdie/data/potion_data.dart';
+import 'package:asciineverdie/src/core/model/equipment_item.dart';
+import 'package:asciineverdie/src/core/model/equipment_slot.dart';
+import 'package:asciineverdie/src/core/model/item_stats.dart';
+import 'package:asciineverdie/src/core/model/treasure_chest.dart';
+import 'package:asciineverdie/src/core/util/deterministic_random.dart';
+
+/// 보물 상자 서비스
+///
+/// 상자 내용물 생성 및 오픈 로직 담당
+class ChestService {
+  ChestService({DeterministicRandom? rng})
+      : _rng = rng ?? DeterministicRandom(DateTime.now().millisecondsSinceEpoch);
+
+  final DeterministicRandom _rng;
+
+  // ==========================================================================
+  // 상수
+  // ==========================================================================
+
+  /// 보상 타입별 확률 (%)
+  static const int _equipmentChance = 40; // 장비 40%
+  static const int _potionChance = 30; // 포션 30%
+  static const int _goldChance = 20; // 골드 20%
+  // 경험치 10% (나머지)
+
+  /// 골드 보상 범위 (레벨 * 배율)
+  static const int _goldPerLevel = 50;
+  static const int _goldVariance = 20;
+
+  /// 경험치 보상 범위 (레벨 * 배율)
+  static const int _expPerLevel = 100;
+  static const int _expVariance = 30;
+
+  /// 포션 수량 범위
+  static const int _minPotionCount = 1;
+  static const int _maxPotionCount = 3;
+
+  // ==========================================================================
+  // 상자 오픈
+  // ==========================================================================
+
+  /// 상자 오픈하여 보상 생성
+  ///
+  /// [playerLevel] 플레이어 레벨 (보상 스케일링용)
+  ChestReward openChest(int playerLevel) {
+    final roll = _rng.nextInt(100);
+
+    if (roll < _equipmentChance) {
+      // 40%: 장비
+      return _generateEquipmentReward(playerLevel);
+    } else if (roll < _equipmentChance + _potionChance) {
+      // 30%: 포션
+      return _generatePotionReward(playerLevel);
+    } else if (roll < _equipmentChance + _potionChance + _goldChance) {
+      // 20%: 골드
+      return _generateGoldReward(playerLevel);
+    } else {
+      // 10%: 경험치
+      return _generateExperienceReward(playerLevel);
+    }
+  }
+
+  /// 여러 상자 오픈
+  List<ChestReward> openMultipleChests(int count, int playerLevel) {
+    final rewards = <ChestReward>[];
+    for (var i = 0; i < count; i++) {
+      rewards.add(openChest(playerLevel));
+    }
+    return rewards;
+  }
+
+  // ==========================================================================
+  // 보상 생성
+  // ==========================================================================
+
+  /// 장비 보상 생성
+  ChestReward _generateEquipmentReward(int playerLevel) {
+    // 랜덤 슬롯 선택
+    final slotIndex = _rng.nextInt(EquipmentSlot.values.length);
+    final slot = EquipmentSlot.values[slotIndex];
+
+    // 희귀도 결정 (상자는 좀 더 좋은 확률)
+    final rarity = _rollChestRarity();
+
+    // 아이템 레벨: 플레이어 레벨 ±2
+    final minLevel = (playerLevel - 2).clamp(1, 999);
+    final maxLevel = playerLevel + 2;
+    final itemLevel = minLevel + _rng.nextInt(maxLevel - minLevel + 1);
+
+    // 아이템 생성
+    final item = EquipmentItem(
+      name: _generateItemName(slot, rarity, itemLevel),
+      slot: slot,
+      level: itemLevel,
+      weight: _calculateWeight(slot, itemLevel),
+      stats: _generateItemStats(slot, itemLevel, rarity),
+      rarity: rarity,
+    );
+
+    debugPrint('[ChestService] Equipment reward: ${item.name} (${rarity.name})');
+    return ChestReward.equipment(item);
+  }
+
+  /// 포션 보상 생성
+  ChestReward _generatePotionReward(int playerLevel) {
+    // 레벨에 맞는 티어 선택
+    final tier = PotionData.tierForLevel(playerLevel);
+
+    // HP/MP 랜덤 선택
+    final isHp = _rng.nextInt(2) == 0;
+    final potion = isHp
+        ? PotionData.getHpPotionByTier(tier)
+        : PotionData.getMpPotionByTier(tier);
+
+    if (potion == null) {
+      // 폴백: 기본 포션
+      return ChestReward.potion('minor_health_patch', 1);
+    }
+
+    // 수량 결정
+    final count =
+        _minPotionCount + _rng.nextInt(_maxPotionCount - _minPotionCount + 1);
+
+    debugPrint('[ChestService] Potion reward: ${potion.name} x$count');
+    return ChestReward.potion(potion.id, count);
+  }
+
+  /// 골드 보상 생성
+  ChestReward _generateGoldReward(int playerLevel) {
+    final baseGold = playerLevel * _goldPerLevel;
+    final variance = _rng.nextInt(_goldVariance * 2 + 1) - _goldVariance;
+    final gold = (baseGold + (baseGold * variance / 100)).round().clamp(10, 99999);
+
+    debugPrint('[ChestService] Gold reward: $gold');
+    return ChestReward.gold(gold);
+  }
+
+  /// 경험치 보상 생성
+  ChestReward _generateExperienceReward(int playerLevel) {
+    final baseExp = playerLevel * _expPerLevel;
+    final variance = _rng.nextInt(_expVariance * 2 + 1) - _expVariance;
+    final exp = (baseExp + (baseExp * variance / 100)).round().clamp(10, 999999);
+
+    debugPrint('[ChestService] Experience reward: $exp');
+    return ChestReward.experience(exp);
+  }
+
+  // ==========================================================================
+  // 헬퍼 메서드
+  // ==========================================================================
+
+  /// 상자 희귀도 롤 (일반 샵보다 좋은 확률)
+  /// Common 50%, Uncommon 30%, Rare 15%, Epic 4%, Legendary 1%
+  ItemRarity _rollChestRarity() {
+    final roll = _rng.nextInt(100);
+    if (roll < 50) return ItemRarity.common;
+    if (roll < 80) return ItemRarity.uncommon;
+    if (roll < 95) return ItemRarity.rare;
+    if (roll < 99) return ItemRarity.epic;
+    return ItemRarity.legendary;
+  }
+
+  /// 아이템 이름 생성
+  String _generateItemName(EquipmentSlot slot, ItemRarity rarity, int level) {
+    final prefix = _getRarityPrefix(rarity);
+    final baseName = _getSlotBaseName(slot);
+    final suffix = level > 10 ? ' +${level ~/ 10}' : '';
+    return '$prefix$baseName$suffix'.trim();
+  }
+
+  String _getRarityPrefix(ItemRarity rarity) {
+    return switch (rarity) {
+      ItemRarity.common => '',
+      ItemRarity.uncommon => 'Fine ',
+      ItemRarity.rare => 'Superior ',
+      ItemRarity.epic => 'Epic ',
+      ItemRarity.legendary => 'Legendary ',
+    };
+  }
+
+  String _getSlotBaseName(EquipmentSlot slot) {
+    return switch (slot) {
+      EquipmentSlot.weapon => 'Keyboard',
+      EquipmentSlot.shield => 'Firewall Shield',
+      EquipmentSlot.helm => 'Neural Headset',
+      EquipmentSlot.hauberk => 'Server Rack Armor',
+      EquipmentSlot.brassairts => 'Cable Brassairts',
+      EquipmentSlot.vambraces => 'USB Vambraces',
+      EquipmentSlot.gauntlets => 'Typing Gauntlets',
+      EquipmentSlot.gambeson => 'Padded Gambeson',
+      EquipmentSlot.cuisses => 'Circuit Cuisses',
+      EquipmentSlot.greaves => 'Copper Greaves',
+      EquipmentSlot.sollerets => 'Static Boots',
+    };
+  }
+
+  /// 스탯 생성
+  ItemStats _generateItemStats(
+    EquipmentSlot slot,
+    int level,
+    ItemRarity rarity,
+  ) {
+    final multiplier = rarity.multiplier;
+    final baseValue = (level * multiplier).round();
+
+    return switch (slot) {
+      EquipmentSlot.weapon => ItemStats(
+          atk: baseValue * 2,
+          criRate: 0.01 * (level ~/ 5),
+          parryRate: 0.005 * level,
+        ),
+      EquipmentSlot.shield => ItemStats(
+          def: baseValue,
+          blockRate: 0.02 * (level ~/ 3).clamp(1, 10),
+        ),
+      EquipmentSlot.helm => ItemStats(
+          def: baseValue ~/ 2,
+          magDef: baseValue ~/ 2,
+          intBonus: level ~/ 10,
+        ),
+      EquipmentSlot.hauberk => ItemStats(def: baseValue, hpBonus: level * 2),
+      EquipmentSlot.brassairts => ItemStats(
+          def: baseValue ~/ 2,
+          strBonus: level ~/ 15,
+        ),
+      EquipmentSlot.vambraces => ItemStats(
+          def: baseValue ~/ 2,
+          dexBonus: level ~/ 15,
+        ),
+      EquipmentSlot.gauntlets => ItemStats(
+          atk: baseValue ~/ 2,
+          def: baseValue ~/ 4,
+        ),
+      EquipmentSlot.gambeson => ItemStats(
+          def: baseValue ~/ 2,
+          conBonus: level ~/ 15,
+        ),
+      EquipmentSlot.cuisses => ItemStats(
+          def: baseValue ~/ 2,
+          evasion: 0.005 * level,
+        ),
+      EquipmentSlot.greaves => ItemStats(
+          def: baseValue ~/ 2,
+          evasion: 0.003 * level,
+        ),
+      EquipmentSlot.sollerets => ItemStats(
+          def: baseValue ~/ 3,
+          evasion: 0.002 * level,
+          dexBonus: level ~/ 20,
+        ),
+    };
+  }
+
+  /// 무게 계산
+  int _calculateWeight(EquipmentSlot slot, int level) {
+    final baseWeight = switch (slot) {
+      EquipmentSlot.weapon => 5,
+      EquipmentSlot.shield => 8,
+      EquipmentSlot.helm => 4,
+      EquipmentSlot.hauberk => 15,
+      EquipmentSlot.brassairts => 3,
+      EquipmentSlot.vambraces => 3,
+      EquipmentSlot.gauntlets => 2,
+      EquipmentSlot.gambeson => 6,
+      EquipmentSlot.cuisses => 5,
+      EquipmentSlot.greaves => 4,
+      EquipmentSlot.sollerets => 3,
+    };
+    return baseWeight + (level ~/ 10);
+  }
+}
diff --git a/lib/src/core/model/treasure_chest.dart b/lib/src/core/model/treasure_chest.dart
new file mode 100644
index 0000000..1f3990e
--- /dev/null
+++ b/lib/src/core/model/treasure_chest.dart
@@ -0,0 +1,115 @@
+import 'package:asciineverdie/src/core/model/equipment_item.dart';
+
+/// 상자 보상 타입
+enum ChestRewardType {
+  /// 장비 아이템
+  equipment,
+
+  /// 포션
+  potion,
+
+  /// 골드
+  gold,
+
+  /// 경험치
+  experience,
+}
+
+/// 상자 내용물 (개봉 결과)
+class ChestReward {
+  const ChestReward._({
+    required this.type,
+    this.equipment,
+    this.potionId,
+    this.potionCount,
+    this.gold,
+    this.experience,
+  });
+
+  /// 장비 보상 생성
+  factory ChestReward.equipment(EquipmentItem item) {
+    return ChestReward._(
+      type: ChestRewardType.equipment,
+      equipment: item,
+    );
+  }
+
+  /// 포션 보상 생성
+  factory ChestReward.potion(String potionId, int count) {
+    return ChestReward._(
+      type: ChestRewardType.potion,
+      potionId: potionId,
+      potionCount: count,
+    );
+  }
+
+  /// 골드 보상 생성
+  factory ChestReward.gold(int amount) {
+    return ChestReward._(
+      type: ChestRewardType.gold,
+      gold: amount,
+    );
+  }
+
+  /// 경험치 보상 생성
+  factory ChestReward.experience(int amount) {
+    return ChestReward._(
+      type: ChestRewardType.experience,
+      experience: amount,
+    );
+  }
+
+  /// 보상 타입
+  final ChestRewardType type;
+
+  /// 장비 (type == equipment일 때)
+  final EquipmentItem? equipment;
+
+  /// 포션 ID (type == potion일 때)
+  final String? potionId;
+
+  /// 포션 수량 (type == potion일 때)
+  final int? potionCount;
+
+  /// 골드 (type == gold일 때)
+  final int? gold;
+
+  /// 경험치 (type == experience일 때)
+  final int? experience;
+
+  /// 장비 보상인지 여부
+  bool get isEquipment => type == ChestRewardType.equipment;
+
+  /// 포션 보상인지 여부
+  bool get isPotion => type == ChestRewardType.potion;
+
+  /// 골드 보상인지 여부
+  bool get isGold => type == ChestRewardType.gold;
+
+  /// 경험치 보상인지 여부
+  bool get isExperience => type == ChestRewardType.experience;
+}
+
+/// 복귀 보상 상자 데이터
+class ReturnChestReward {
+  const ReturnChestReward({
+    required this.hoursAway,
+    required this.chestCount,
+    required this.bonusChestCount,
+  });
+
+  /// 떠나있던 시간 (시간 단위)
+  final int hoursAway;
+
+  /// 기본 상자 개수
+  final int chestCount;
+
+  /// 보너스 상자 개수 (광고 시청 시 추가)
+  final int bonusChestCount;
+
+  /// 총 상자 개수 (광고 포함)
+  int get totalChests => chestCount + bonusChestCount;
+
+  /// 보상이 있는지 여부
+  bool get hasReward => chestCount > 0;
+}