Two new bosses this time, including the notorious Mandragoras from XII. Can't seem to find info about either bosses as well, so will go off the top of my head. There's also a 3rd difficulty of 240.

Multiplayer Enemy AI by /u/TFMurphy

BOSS: Ultros - Opera House (VI)

Difficulties: 160 (Ultimate ), 200 (Apocalypse) and 240 (Apocalypse )

Mastery Conditions:

• Win with 4 or more party members alive.
• Exploit Ultros' weakness to Fire-elemental attacks.
• Exploit Ultros' weakness to Lightning-elemental attacks.

Overview:

• Every time he is killed, he will revive and reappear on a different part of the opponent's half of the field. This happens 4 times after he is killed the first time, for a total of 5 phases.
• He is weak to Lightning and Fire, but he has a 100% Counter Firaga if hit with Fire-elemental attacks (nasty mastery condition there).
• Uses a mix of physical and magical attacks, though his magic are mostly limited to Fire, Lightning, and Water-elemental attacks.
• Capable of casting self-Haste, Protect, Shell, often as counters.

Tips:

• The best way to hit his Fire-elemental weakness is to use a Soul Break.
• Shantotto's BSB/SSB are both fantastic here. They hit Fire/Ice/Lightning-elemental weaknesses, thus not triggering his Counter Firaga. With her BSB, her commands should prioritize Lightning-elemental since she has En-Lightning.
• Indomitable Blade deals with Counter Firaga handily.
• Note that debuffs wear off every time he revives, so be prepared to reapply them immediately.
• Bring Banishing Strike/Dispel to deal with Counter Haste/Protect/Shell. I can't remember if he has Reflect immunity or not, but that is also worth a shot (at the cost of not being able to use standard mage spells).

BOSS: Mandragoras (XII)

Difficulties: 160 (Ultimate ), 200 (Apocalypse) and 240 (Apocalypse )

Mastery Conditions:

• Win with 4 or more party members alive.
• Exploit Mandragora's Prince weakness to Fire-elemental attacks.
• Exploit Alraune King's weakness to Holy-elemental attacks..

Overview:

• The notorious Mandragoras. There are five of them, and they all start Hasted.
• When they are killed individually, they are capable of using a desperation ability that buffs the other remaining Mandragoras (either stats or Protect/Shell/Haste).
• They each have differing elemental weaknesses, as well as status vulnerabilities. From top to bottom, in counter-clockwise order:
  • Onion Queen - weak to Earth, and vulnerable to Confuse.
  • Mandragora Prince - weak to Fire. Not vulnerable to any status effects.
  • Alraune King - weak to Holy, vulnerable to Stop.
  • Topstalk - weak to Water, vulnerable to Blind.
  • Pumpkin Star - weak to Dark, vulnerable to Sleep.
• Lots of status effects in this fight. Look forward to Sleep, Confuse, Silence, Slow, Poison, among some of them.

Tips:

• No magic damage in this fight. Leave Shellga or magic mitigation at home.
• AoE debuff Soul Breaks such as Cait Sith's Toy Soldiers or Faris' Sea Lord's Broadside are fantastic for this fight. Faris can become especially useful if dived for Dancer 5, but otherwise someone else can always cover that slot (a Tyro on your team maybe?)
• Hope's BSB2 allows you to simultaneously Dispel all of the Mandragoras at once, so it's worth bringing him here for that and hitting Alraune King's Holy-elemental weakness.
• Ramza's BSB is also fantastic here - it grants a party DEF 100% on entry, hits all enemies, and comes with a Banishing Strike C1. Be more aware when pubbing - they may not always be bringing Shout.
• Tyro's USB and Vanille's USB are the only sources of Astra for Global to date, so both will help out a fair bit.