diff --git a/src/Battling/Flow/TurnHandler.cpp b/src/Battling/Flow/TurnHandler.cpp
index ff469f0..62a56f7 100644
--- a/src/Battling/Flow/TurnHandler.cpp
+++ b/src/Battling/Flow/TurnHandler.cpp
@@ -50,8 +50,8 @@ void TurnHandler::ExecuteChoice(const ArbUt::BorrowedPtr<BaseTurnChoice>& choice
     if (battle->HasEnded()) {
         return;
     }
-    // If the user is fainted, we don't want to execute its choice.
-    if (user->IsFainted()) {
+    // If the user is not usable, we don't want to execute its choice.
+    if (!user->IsUsable()) {
         return;
     }
     // If the user is not in the field, we don't want to execute its choice.
diff --git a/src/Battling/Library/ExperienceLibrary.cpp b/src/Battling/Library/ExperienceLibrary.cpp
index 58ab90d..0931347 100644
--- a/src/Battling/Library/ExperienceLibrary.cpp
+++ b/src/Battling/Library/ExperienceLibrary.cpp
@@ -4,7 +4,7 @@
 void CreatureLib::Battling::ExperienceLibrary::HandleExperienceGain(
     CreatureLib::Battling::Creature* faintedMon,
     const std::unordered_set<ArbUt::BorrowedPtr<Creature>>& opponents) const {
-    for (auto opponent : opponents) {
+    for (const auto& opponent : opponents) {
         if (opponent->IsFainted())
             continue;
         if (!opponent->AllowedExperienceGain())
diff --git a/src/Battling/Models/BattleParty.hpp b/src/Battling/Models/BattleParty.hpp
index 6415414..1f83a07 100644
--- a/src/Battling/Models/BattleParty.hpp
+++ b/src/Battling/Models/BattleParty.hpp
@@ -34,7 +34,7 @@ namespace CreatureLib::Battling {
             for (const auto& creature : p) {
                 if (creature == nullptr)
                     continue;
-                if (creature->IsFainted())
+                if (!creature->IsUsable())
                     continue;
                 if (creature->IsOnBattleField())
                     continue;
diff --git a/src/Battling/Models/BattleSide.cpp b/src/Battling/Models/BattleSide.cpp
index f9543ac..53f46e2 100644
--- a/src/Battling/Models/BattleSide.cpp
+++ b/src/Battling/Models/BattleSide.cpp
@@ -10,7 +10,7 @@ bool BattleSide::AllPossibleSlotsFilled() const {
     try {
         for (size_t i = 0; i < _creatures.Count(); i++) {
             auto c = _creatures[i];
-            if (!c.HasValue() || c.GetValue()->IsFainted()) {
+            if (!c.HasValue() || !c.GetValue()->IsUsable()) {
                 if (_battle->CanSlotBeFilled(_index, i)) {
                     return false;
                 }
diff --git a/src/Battling/Models/Creature.cpp b/src/Battling/Models/Creature.cpp
index 70675f5..3de7220 100644
--- a/src/Battling/Models/Creature.cpp
+++ b/src/Battling/Models/Creature.cpp
@@ -143,6 +143,8 @@ namespace CreatureLib::Battling {
         this->_boostedStats.SetStat(stat, s);
     }
 
+    bool Creature::IsUsable() const noexcept { return !this->IsFainted(); }
+
     bool Creature::IsFainted() const noexcept { return this->_currentHealth == 0; }
 
     void Creature::OnFaint() {
diff --git a/src/Battling/Models/Creature.hpp b/src/Battling/Models/Creature.hpp
index 5b466d4..820add5 100644
--- a/src/Battling/Models/Creature.hpp
+++ b/src/Battling/Models/Creature.hpp
@@ -122,6 +122,8 @@ namespace CreatureLib::Battling {
         const CreatureLib::Library::TalentIndex& GetRealTalent() const noexcept { return _talentIndex; }
         const ArbUt::StringView& GetActiveTalent() const;
 
+        /// Are we allowed to use this creature in a battle?
+        [[nodiscard]] virtual bool IsUsable() const noexcept;
         [[nodiscard]] bool IsFainted() const noexcept;
         [[nodiscard]] const std::vector<uint8_t>& GetTypes() const noexcept;
         [[nodiscard]] bool HasType(uint8_t type) const noexcept;
diff --git a/src/Battling/Models/CreatureParty.hpp b/src/Battling/Models/CreatureParty.hpp
index 0d71f59..1d4dc57 100644
--- a/src/Battling/Models/CreatureParty.hpp
+++ b/src/Battling/Models/CreatureParty.hpp
@@ -35,7 +35,7 @@ namespace CreatureLib::Battling {
             for (Creature* c : _party) {
                 if (c == nullptr)
                     continue;
-                if (c->IsFainted())
+                if (!c->IsUsable())
                     continue;
                 return true;
             }
diff --git a/src/Precompiled.hxx b/src/Precompiled.hxx
index aebe9fd..1e34b8a 100644
--- a/src/Precompiled.hxx
+++ b/src/Precompiled.hxx
@@ -10,6 +10,7 @@
 #include <exception>
 #include <memory>
 #include <numeric>
+#include <optional>
 #include <sstream>
 #include <stdexcept>
 #include <string>