>>17832 (OP)You have to summon the djinn companions for this fight, also make sure to consume pork products and alcohol before the battle (take INT-boosting meds to counteract the drunk status effect on your Intelligence). Avoid the month of Ramadan when challenging the boss, he gets a significant damage and defense boost during this time.
Obtain artifacts that protect against Holy damage. Also make sure to train your Illusion stat as a whole. As a rule of thumb, don't waste your memory slots with any spells/incantations of Abrahamic origin, Allah naturally possesses a strong (90+%) resist to all such damage, might even reflect some of it back at you. Consider Buddhist or Pagan-origin attacks as an alternative. The Nordic family in particular is insane for DPS, and Buddhism is great for healing/protection.