fix(Scripts/SunwellPlateau): Move Dark Fiend from SmartAI to ScriptedAI with corrected despawn behavior (#21910)

data/sql/updates/pending_db_world/rev_1744470192125627678.sql

@@ -0,0 +1,5 @@
+-- Remove SmartAI from dark fiend to ScriptedAI (c++)
+UPDATE `creature_template` SET
+  `AIName` = '',
+  `ScriptName` = 'npc_dark_fiend'
+WHERE `entry` = 25744;

src/server/scripts/EasternKingdoms/SunwellPlateau/boss_muru.cpp

@@ -51,7 +51,14 @@ enum Spells
     SPELL_BLACK_HOLE_SUMMON_VISUAL2     = 46247,
     SPELL_BLACK_HOLE_VISUAL2            = 46235,
     SPELL_BLACK_HOLE_PASSIVE            = 46228,
-    SPELL_BLACK_HOLE_EFFECT             = 46230
+    SPELL_BLACK_HOLE_EFFECT             = 46230,
+
+    // Dark Fiend Spells
+    SPELL_DARK_FIEND_APPEARANCE         = 45934,
+    SPELL_DARK_FIEND_SECONDARY          = 45936,
+    SPELL_DARK_FIEND_TRIGGER            = 45944
+    // It is currently unkown why Dark Fiend Casts this or what it should do
+    //SPELL_DARK_FIEND_TRIGGER_SINGLE   = 45943
 };
 
 struct boss_muru : public BossAI
@@ -67,6 +74,17 @@ struct boss_muru : public BossAI
         me->m_Events.KillAllEvents(false);
     }
 
+    void MoveInLineOfSight(Unit* who) override
+    {
+        // Radius of room is ~38.5f this might need adjusting a bit
+        // Radius ~36.0 is right inside
+        // Radius 20.0 is outer circle
+        if (!me->IsInCombat() && who->IsPlayer() && me->IsWithinDistInMap(who, 25.0f))
+        {
+            me->SetInCombatWithZone();
+        }
+    }
+
     void JustEngagedWith(Unit* who) override
     {
         BossAI::JustEngagedWith(who);
@@ -174,6 +192,76 @@ struct boss_entropius : public ScriptedAI
     }
 };
 
+struct npc_dark_fiend : public ScriptedAI
+{
+    npc_dark_fiend(Creature* creature) : ScriptedAI(creature) { }
+
+    void Reset() override
+    {
+        _lastVictimGUID.Clear();
+        _spellCast = false;
+
+        me->SetReactState(REACT_PASSIVE);
+        DoCast(me, SPELL_DARK_FIEND_APPEARANCE);
+        DoCast(me, SPELL_DARK_FIEND_SECONDARY);
+
+        me->m_Events.AddEventAtOffset([this]() {
+            me->SetReactState(REACT_AGGRESSIVE);
+            if (Unit* target = SelectTargetFromPlayerList(200.0f, 0, true))
+            {
+                AttackStart(target);
+                me->AddThreat(target, 100000.0f);
+            }
+        }, 1s, 2s);
+    }
+
+    void DamageTaken(Unit* /*attacker*/, uint32& damage, DamageEffectType /*damagetype*/, SpellSchoolMask /*schoolMask*/) override
+    {
+        if (damage >= me->GetHealth())
+            damage = me->GetHealth() - me->GetMaxHealth() * 0.01f;
+    }
+
+    void UpdateAI(uint32 /*diff*/) override
+    {
+        if (!me->HasAura(SPELL_DARK_FIEND_APPEARANCE))
+        {
+            me->DespawnOrUnsummon();
+            return;
+        }
+
+        // Check if victim has changed or disappeared
+        Unit* currentVictim = me->GetVictim();
+        ObjectGuid currentVictimGUID = currentVictim ? currentVictim->GetGUID() : ObjectGuid::Empty;
+
+        if (_lastVictimGUID != currentVictimGUID)
+        {
+            // If had a victim before but now it's gone
+            if (!_lastVictimGUID.IsEmpty() && currentVictimGUID.IsEmpty())
+                me->DespawnOrUnsummon();
+
+            _lastVictimGUID = currentVictimGUID;
+        }
+
+        if (!UpdateVictim())
+            return;
+
+        if (!_spellCast && currentVictim && me->IsWithinMeleeRange(currentVictim, 2.0f))
+        {
+            DoCast(me, SPELL_DARK_FIEND_TRIGGER);
+            _spellCast = true;
+            me->m_Events.AddEventAtOffset([this]() {
+                me->DespawnOrUnsummon();
+            }, 1s);
+        }
+
+        DoMeleeAttackIfReady();
+    }
+
+private:
+    ObjectGuid _lastVictimGUID;
+    bool _spellCast;
+};
+
 struct npc_singularity : public NullCreatureAI
 {
     npc_singularity(Creature* creature) : NullCreatureAI(creature) { }
@@ -270,7 +358,7 @@ class spell_muru_darkness_aura : public AuraScript
 
     void OnPeriodic(AuraEffect const* aurEff)
     {
-        if (aurEff->GetTickNumber() == 3)
+        if (aurEff->GetTickNumber() == 2)
             for (uint8 i = 0; i < 8; ++i)
                 GetUnitOwner()->CastSpell(GetUnitOwner(), SPELL_SUMMON_DARK_FIEND + i, true);
     }
@@ -390,6 +478,7 @@ void AddSC_boss_muru()
     RegisterSunwellPlateauCreatureAI(boss_muru);
     RegisterSunwellPlateauCreatureAI(boss_entropius);
     RegisterSunwellPlateauCreatureAI(npc_singularity);
+    RegisterSunwellPlateauCreatureAI(npc_dark_fiend);
 
     RegisterSpellScript(spell_muru_summon_blood_elves_periodic_aura);
     RegisterSpellScript(spell_muru_darkness_aura);