A Persona that repels Physical (such as Rangda) will give you complete immunity to the mini-boss as it will be unable to damage Yu and get the attack reflected back at itself.. Question about Secret Laboratory Do I need to beat the boss on Floor B4F in order to complete the castle/dungeon? I know on the previous castle you had to get a key item in order to fight the boss, question is, it it the same for the secret laboratory boss?
For Persona 4 Golden on the PlayStation Vita, a GameFAQs Q&A question titled "How do I get past Secret Laboratory, B6F?".. For Shin Megami Tensei: Persona 4 on the PlayStation 2, a GameFAQs Q&A question titled "Where can I find the ID card for the Secret Laboratory ?".