Will of Shahram and Holy Strength should have separate aura slot per caster.

https://www.youtube.com/watch?v=rakfLOlB-xc

sql/migrations/20231205020742_world.sql

@@ -0,0 +1,21 @@
+DROP PROCEDURE IF EXISTS add_migration;
+delimiter ??
+CREATE PROCEDURE `add_migration`()
+BEGIN
+DECLARE v INT DEFAULT 1;
+SET v = (SELECT COUNT(*) FROM `migrations` WHERE `id`='20231205020742');
+IF v=0 THEN
+INSERT INTO `migrations` VALUES ('20231205020742');
+-- Add your query below.
+
+
+-- Will of Shahram and Holy Strength should have separate aura slot per caster.
+UPDATE `spell_template` SET `customFlags` = (`customFlags` | 4096) WHERE `entry` IN (16598, 20007);
+
+
+-- End of migration.
+END IF;
+END??
+delimiter ; 
+CALL add_migration();
+DROP PROCEDURE IF EXISTS add_migration;

src/game/Objects/Unit.cpp

@@ -3235,6 +3235,10 @@ bool Unit::AddSpellAuraHolder(SpellAuraHolder* holder)
             // Skip channeled spells (Arcane missile, ...) so two casters can channel at the same time
             if (aurSpellInfo->IsChanneledSpell())
                 continue;
+
+            if (aurSpellInfo->Custom & SPELL_CUSTOM_SEPARATE_AURA_PER_CASTER)
+                continue;
+
             bool stop = false;
 
             for (int32 i = 0; i < MAX_EFFECT_INDEX && !stop; ++i)
@@ -3243,10 +3247,6 @@ bool Unit::AddSpellAuraHolder(SpellAuraHolder* holder)
                 if (!foundHolder->m_auras[i] || !holder->m_auras[i])
                     continue;
 
-                // Croise
-                if (aurSpellInfo->Id == 20007)
-                    break;
-
                 // m_auraname can be modified to SPELL_AURA_NONE for area auras, use original
                 AuraType aurNameReal = AuraType(aurSpellInfo->EffectApplyAuraName[i]);
 

src/game/Spells/SpellDefines.h

@@ -886,6 +886,7 @@ enum SpellAttributesCustom
     SPELL_CUSTOM_AURA_APPLY_BREAKS_STEALTH  = 0x200,     // Stealth is removed when this aura is applied
     SPELL_CUSTOM_NOT_REMOVED_ON_EVADE       = 0x400,     // Aura persists after creature evades
     SPELL_CUSTOM_SEND_CHANNEL_VISUAL        = 0x800,     // Will periodically send the channeling spell visual kit
+    SPELL_CUSTOM_SEPARATE_AURA_PER_CASTER   = 0x1000,    // Each caster has his own aura slot, instead of replacing others
 };
 
 // Custom flags assigned by the core based on spell template data