I fought it four times on the test server. We fought them in sequence, too. Things can be different if you do them in other order.
1- Lion
2- Prishe
3- Nashimeira
4- Lilisette
5- Mumor
Things I remember from it:
Lion isn't as bad as she looks like. Fight her normally. I don't remember anything menacingly difficult about her.
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Prishe can do benedition or hundred fists on you. I think I only seen she do benediction once. She do like her hundred fists though. I saw her do it twice. There's been two times we killed her so fast she were not able to use her 2hours at all.
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Nashmeira likes to run around through the zone pathetically punching people and while she doesn't look very intimidating, she has a move called "Imperial Authority" which kills on a single hit if it lands.
Ovjang is a attack type mage puppet and can 1 shot a melee easily with high tier spells or wreak havok on a party with GAs. You want it down ASAP.
Mnejing (white puppet) is WHM type and won't be as bad as the Ovjang. If you have someone with blink/utsu you can kite ovjang and kill Mnejing first.
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Lilisette isn't anything scary until she trances and splits in two. Fake one aways take 0 damage. Make sure to not let the fake one break havok on your mages.
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Mumor fight has "two stages" and on second stage she uses a move which gives her butterfly wings, she flies and spins around (she uses that move on the current summer event scene btw) and gives a AoE damage to everyone close. Anyone out of the AoE range get killed instandly. No questions asked. Have your mages run in and deal with the blow.
Win all five, a sixth rune activates, where you can fight all six at once. Frantic battle.
Hope this helps a bit. And good luck with the fight !
P.S.: Beating 6 vs 6 fight grants you a second title. And while the test server one gave no prizes, I don't know if the one on real sever gives out any prizes. I did like the title, though.