GoS final boss

Phase 1 - Rotating sisters
- Ana regens 999 HP for two turns in every six turns. It shouldn't be too difficult to outdamage that. There is no need to rush through this battle. Mokou does excellent damage. Marisa and Patchy can also hit weaknesses.
- Ana hits hard. Hinotori Skydance helps direct the attacks to the center, where a tank like Mokou can be placed.
- Muscle Revolution still hits really hard. Reimu can block all physical attacks.
- lolbiotopos
- Lithos has annoying spells that inflict status. Sanae can Res++ and also cure status. Reimu can negate it.
- Maid Summons. As long as everything is single-target, no damage will leak to summons like the alligator or the snake. As for the maids, well, I guess I'd have to interrupt damaging the sisters and go for the maids.

Phase 2 - Three Sisters time limit
- Every third turn seems to be dedicated to Prayer. Three Prayers will screw me over. Sakuya's Private Square (with or without Paparazzi) can skip Prayers.
- Minus deals 666 damage. Reviver needed.
- Next form is tough, so this is a good time to set up for the final phase.

Phase 3 - FF
- Uses some pretty big spells. Satori can turn them around with Reflect Wall.
- Uses some hard-hitting attacks too.
- Inflicts status. Sanae can Res++ or Dispel
For all the above, Alice as a unit can Little Legion to prevent spreading damage. Sanae as a unit can revive unfortunate victims. Nitori can negate the effects of a single attack, both as a unit and as a commander.
- Absorbs Land to deal 777 damage to everyone and heal 10000 HP. Patchy can neutralize the Land.
- Foreign God, weak to Dark. Endark PATK++ Youmu can dish out heavy damage.

Character niches -
- Reimu: Barriers that can negate physical attacks, magical attacks, or status effects. Can also heal or cure status, but they all have some cooldown. Can also attack with LGT magic and raise LGT Land, both of which are useless atm. Barriers are amazing in Phase 1 since the threatening spells are pre-warned. Barriers are still useful in Phase 3 though.

- Marisa: Fast and powerful magic. Three basic elements. Can hit all sisters super-effectively. Can keep two levels of each element to handle cooldowns of the powerful ones. Best for Phase 1.

- Sanae: Healing, reviving, dispelling, stat-boosting. She's the only one who can do all of those without cooldowns (including Source of Rains, the party revive+dispel), though Byakuren wouldn't mind the stat-boosting cooldown. Her revive niche is particularly important, and so, she would be better off in the tougher battle i.e. Phase 3.

- Aya: Manipulate turn order. As a commander, Paparazzi can skip the opponent's turn entirely when paired with Private Square. As a unit, she has a bomb that improves EVA of all allies. This can be incredibly useful in Phase 1, where the biggest threats are Ana's physical (dodgeable) attacks and the spellcards, the latter of which can be negated by Reimu anyway.

- Sakuya: Her PATK may be huge, but her ACC is not too great, and FMR does not help matters. Likely won't be able to hit FF's high EVA. However, Private Square can be very useful. It can delay the time limit in Phase 2, and it can grant one person a few free turns in the private square during the party switch, allowing free set-up. Finally, Private Square can completely skip an enemy's turn when used alongside Paparazzi.

- Patchouli: Powerful magic with no cooldown. All seven non-physical elements. This makes her even better than Marisa for Phase 1. However, she can also manipulate Land, thus preventing Void Cavitation from activating in Phase 2. She can also set up fields that boost/weaken certain elements, but DRK is not amongst them.

- Nitori: Chasers help a lot when there are multiple attacks of the same element going around. Unfortunately though, Patchy likely won't be in Phase 1 so the chasers aren't worth using if it's just Marisa. Elemental bombs have annoying cooldowns and damage leaks. Elemental bullets won't help since the weakness keeps changing. As a commander though, she can provide Optical Camouflage, which is basically Starlight Barrier for a single turn.

- Alice: Wall. She can Parrar on a column, absorb all attacks with Little Legion, bait the enemy with Hourai Doll, cover allies with London or Tibetan dolls, and improve her own defenses with Holland and Russian dolls respectively. Walling has higher demand in Phase 3.

- Satori: She can use elemental attacks in Phase 1 to hit the sisters' weakness. She can also Starlight Barrier and Leaf Shield, which are useful for all phases. Reflect Wall is particularly useful for Phase 3.

- Youmu: Her only niche is attacking. Paschal is so good that she should focus on destroying phase 3 with Endark and PATK++.

- Byakuren: She is the only one that can Endark, which lets the boss get hit super-effectively by Youmu's powerful skills. She can also boost stats, but they're all single-target. Which should be fine if Youmu is the only attacker. Amplifying Scroll is always nice. She might also proc lucky stat drops on the enemy.

- Mokou: FUJIYAMA VOLCANO!!! Destroys the first phase. She can also revive people as a Commander but Fujiyama Volcano is just too good. She can grant Reraise as a unit but Vortex keeps mocking that.