Sadly the game seems not to recognize replenishing Shelke AA towards the orb. She has to replenish S1 and S2 to uptick the orb. So I just went for a 1T run instead.
The idea is to use Shelke to charge Ifrit summon with Raines call, as well as to uptick the orb +20 once. After that I swap her for Selphie to apply Rapture and go to town with Terra.
Timestamp
Party setup at 7:45
Terra has a 2/5 UW, Cissnei has a 5/5 UW
Raines LDCA is mandatory to charge summon meter.
If you don't have Leo LDCA use Cait Sith
If you don't have Rydia LDCA try WoL LDCA
0:00 Setup
Reset until Shelke goes first. Use both Raines call and S1 to launch three times. Then spam AA until Ifrit summon is charged.
Pop summon
1:32 Summon Mode
Shelke uses S2, then LD which should uptick the orb
Swap her out for Selphie and use LD
Cissnei uses Leo LDCA and LD
Terra uses LD
After summon mode, have Terra use Rydia LDCA. If you have WoL LDCA equipped use this only before she goes to BT mode.
Bring boss as close as possible to 50% then pop BT mode
4:31 Terra BT mode
Bring boss below 29% here
6:17 Finishing Up
After BT mode boss will get three instant turns but Rydia LDCA will protect you. Then just continue Terra's Meltdown spam to the end.
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