Hi, I'm Treeston, and welcome to Combat PR Prep Refactors.

Today, we're moving UNIT_FLAG_IMMUNE_TO_PC and UNIT_FLAG_IMMUNE_TO_NPC to higher-level abstraction so combat manager can react to it.
New methods on Unit:
- void SetImmuneTo<All/PC/NPC>(apply, keepCombat = false);
- bool IsImmuneTo<All/PC/NPC>() const;

(cherry picked from commit 74af880217)

src/server/game/Spells/SpellEffects.cpp

@@ -1992,8 +1992,7 @@ void Spell::EffectSummonType(SpellEffIndex effIndex)
                     summon->SelectLevel();       // some summoned creaters have different from 1 DB data for level/hp
                     summon->SetNpcFlags(NPCFlags(summon->GetCreatureTemplate()->npcflag & 0xFFFFFFFF));
                     summon->SetNpcFlags2(NPCFlags2(summon->GetCreatureTemplate()->npcflag >> 32));
-
-                    summon->AddUnitFlag(UnitFlags(UNIT_FLAG_IMMUNE_TO_PC | UNIT_FLAG_IMMUNE_TO_NPC));
+                    summon->SetImmuneToAll(true);
 
                     summon->AI()->EnterEvadeMode();
                     break;