diff --git a/data/sql/updates/pending_db_world/rev_1785749167609908400.sql b/data/sql/updates/pending_db_world/rev_1785749167609908400.sql
new file mode 100644
index 0000000000..7b296bbc31
--- /dev/null
+++ b/data/sql/updates/pending_db_world/rev_1785749167609908400.sql
@@ -0,0 +1,2 @@
+-- Runic Colossus and Ancient Rune Giant spawn immune to players until activated (sniff build 68887)
+UPDATE `creature_template` SET `unit_flags` = `unit_flags` | 256, `VerifiedBuild` = 68887 WHERE `entry` IN (32872, 32873);
diff --git a/src/server/scripts/Northrend/Ulduar/Ulduar/boss_thorim.cpp b/src/server/scripts/Northrend/Ulduar/Ulduar/boss_thorim.cpp
index 4cd6b94967..01748f8058 100644
--- a/src/server/scripts/Northrend/Ulduar/Ulduar/boss_thorim.cpp
+++ b/src/server/scripts/Northrend/Ulduar/Ulduar/boss_thorim.cpp
@@ -457,11 +457,11 @@ struct boss_thorim : public BossAI
                 if (GameObject* go = GetThorimObject(DATA_THORIM_LEVER))
                     go->RemoveGameObjectFlag((GameObjectFlags)48);
 
-                // Iron Ring Guard / Iron Honor Guard spawn with UNIT_FLAG_IMMUNE_TO_PC
+                // Iron Ring Guards and the Runic Colossus spawn with UNIT_FLAG_IMMUNE_TO_PC until the arena event starts
                 summons.DoForAllSummons([](WorldObject* obj)
                 {
                     if (Creature* c = obj->ToCreature())
-                        if (c->GetEntry() == NPC_IRON_RING_GUARD || c->GetEntry() == NPC_IRON_HONOR_GUARD)
+                        if (c->EntryEquals(NPC_IRON_RING_GUARD, NPC_RUNIC_COLOSSUS))
                             c->RemoveUnitFlag(UNIT_FLAG_IMMUNE_TO_PC);
                 });
 
@@ -1288,6 +1288,10 @@ struct boss_thorim_runic_colossus : public ScriptedAI
                 if (Creature* cr = me->GetInstanceScript()->GetCreature(BOSS_THORIM))
                     cr->AI()->Talk(SAY_SPECIAL_2);
             }
+
+            // The Ancient Rune Giant stays immune to players until the colossus falls
+            if (Creature* giant = me->FindNearestCreature(NPC_ANCIENT_RUNE_GIANT, 200.0f))
+                giant->RemoveUnitFlag(UNIT_FLAG_IMMUNE_TO_PC);
         }
 
         void JustEngagedWith(Unit*) override