diff --git a/src/naxx40Scripts/boss_kelthuzad_40.cpp b/src/naxx40Scripts/boss_kelthuzad_40.cpp
index 2e5befe..0d64133 100644
--- a/src/naxx40Scripts/boss_kelthuzad_40.cpp
+++ b/src/naxx40Scripts/boss_kelthuzad_40.cpp
@@ -741,10 +741,32 @@ public:
     }
 };
 
+
+class spell_kelthuzad_dark_blast : public SpellScript
+{
+    PrepareSpellScript(spell_kelthuzad_dark_blast);
+
+    void CalculateDamage(SpellEffIndex /*effIndex*/)
+    {
+        Unit* caster = GetCaster();
+        if (!caster || (caster->GetMap()->GetDifficulty() != RAID_DIFFICULTY_10MAN_HEROIC))
+        {
+            return;
+        }
+        SetEffectValue(urand(1750,2250));
+    }
+
+    void Register() override
+    {
+        OnEffectLaunchTarget += SpellEffectFn(spell_kelthuzad_dark_blast::CalculateDamage, EFFECT_0, SPELL_EFFECT_SCHOOL_DAMAGE);
+    }
+};
+
 void AddSC_boss_kelthuzad_40()
 {
     new boss_kelthuzad_40();
     new boss_kelthuzad_minion_40();
 //    new spell_kelthuzad_frost_blast();
 //    new spell_kelthuzad_detonate_mana();
+    RegisterSpellScript(spell_kelthuzad_dark_blast);
 }