44m HP? That just means one extra summon mode after Machina's BT mode. Machina as always didn't disappoint :)
Timestamp
Party setup at 7:48
If you don't have Leo LDCA try Cait Sith
If you don't have Rydia LDCA use WoL LDCA
If you don't have Fang LDCA use Edward LDCA
I unequipped BRV Initiative and Peridot Thunderflash Lite Passive from Garnet.
0:00 Phase 1 (100-79%)
Reset until you get turn order of Machina, Garnet and Cissnei
Use Machina Awakening until Garnet overhead goes off. This is mainly to charge summon meter a bit.
Machina goes BT+
Garnet goes BT+, AA, Leo LDCA and then S2
Cissnei goes AA, Rydia LDCA then LD
Boss should be at 80% or close.
Use Machina Fang LDCA to bring boss to 79%
2:48 Phase 2 Machina BT mode time
Boss will warp turns at 79% but will be disabled due to Fang LD debuff.
You'll still be on Machina's turn. I used Fang base call just for some additional damage and up uptick Garnet's overhead and then popped BT mode.
You'll be able to bring boss very close to 30% with this BT mode
6:09 Phase 3 Summon Mode
When you get out of Summon Mode, boss will warp turns but every hit will miss you due to Rydia LDCA. The attacks will also trigger Machina's counter and will continue to charge the summon meter.
I ended up nicely having a full summon meter by the end of the turn warp.
You'll be at Garnet's turn, use Leo base call then pop summon to finish off the boss
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