Sorry I haven't really been on top of these. Long weekend, late nights playing Persona 5, etc.

Multiplayer Enemy AI by /u/TFMurphy

BOSS: Hein (III)

Difficulties: 160 (Ultimate ) and 200 (Apocalypse)

Mastery Conditions:

• Win with 4 or more party members alive.
• Reduce Hein's RES.
• Reduce Hein's MAG.

Overview:

• At any one time, will have a weakness to Fire, Ice or Lightning. Resists all other elements otherwise.
• Has a 100% chance to counter physical attacks with AoE Confuse.
• As the battle goes on, has a higher chance to counter BLK abilities with AoE Sleep.
• Mainly uses Fire, Ice or Lightning magic otherwise.

Tips:

• Leave physicals at home. Use Dances to debuff Hein.
• The only status effect you should worry about here are Sleep. But it has a very low chance to proc anyway.
• Grand Cross is great for this fight, as a lot of his abilities are BLK. Celes with Indomitable Blade works too, as you can gear her for magic, but she will only have access to 4* BLK.
• Elemental resistance for everyone else is a great idea.
• A reminder to all Y'shtola users that auto-attacks cannot remove Confuse through HP Bubble, if you do get hit with it. Remember to bring Esuna or Ultra Cure to deal with it.