First, credit to Alkatrev for finding and posting the initial petrify cheese, which is mostly a 5T petrify variant (said youtube comment has a detailed description of what the rotation is). That said, between some heavy testing on discord between myself and u/FlipMethod (in addition to other ppl noticing stuff), it was discovered that there were AI breakage that can lead to disjointing the rotation at times (usually post-threshold), leading to death. Instead, this post will instead show two things, (1) an alternative method that uses a 3T rotation w/ the option to get high morale (eventually), and (2) the AI breakage explanation in question, or at least to the best of my explanation with what was discovered. Without further ado...

CoW 3-3 Petrify Cheese (3T Variant)

What You Need

• Shadow Lord w/ Immortal Justice fully awakened, using an elemental weapon (dark preferably) and at 100% passive elemental resistance for that weapon element. If anyone on the team has passive evasion, then SL will also need to be built for accuracy
• Three 1-T hiders, all of them needs to be equipped with some way to auto-generate esper gauge so that you have full gauge by T2, then every 3 turns afterwards (over build for this as some of them might be dead/petrified at times).
  • 1 w/ Pheonix
  • other 2 w/ a way to AoE cure petrify (eg: Rikku's Pouch)
• Some way to fill morale (either directly or indirectly)

Rotation (3T)

Actions must be done in the order listed.

Turn 1

1. Fill morale w/ non-hiders.
2. Hide all hiders.
3. Deal damage.
4. (Optional) Have Shadow Lord use 3x Violent Rupture on the party.

Note: Barring the first turn and immediately after a threshold, the only action you will need to do is hide due to everyone else floor tanking at this point.

Turn 2

1. Pheonix summon
2. Hide w/ hiders

When boss does his move this turn, every non-hider the pheonix holder will be petrified.

Turn 3

1. Cure petrify on party.
2. If any morale stop or imperil was used last turn (Motionless and Pallid Despair, respectively), use Remedial Will (player morale ability)
3. Fill morale w/ non-hiders.
4. Hide all hiders.
5. Depends on whether you want to damage or build morale this turn. If doing damage this turn, do that. If building morale instead, have Shadow Lord use 3x Violent Rupture on the party.

You'll most likely cross the threshold on this turn. If for some reason you cross it a different turn somehow, then immediately go to T1 after the boss does its threshold stuff (do not pass "Go", do not collect $200).

Video Example

https://www.youtube.com/watch?v=WAZdtYhP1lI (FlipMethod)

Why this works

This abuses the petrify mechanic. When an unit gets petrified here, they will take no damage from upcoming attack, and can immediately act on following turns upon being cured. And because the boss has a guaranteed petrify (assuming no anti-petrify buffs) before it does its attacks, we can use the second turn to revive everyone and setup for damage the following turn.

You'll also notice that I have Shadow Lord occasionally kill off all the non-hiders barring himself. This is because of how the morale mechanics works for KO's. When the boss KO's your party, you get hit for morale for each unit you lost. However, if you KO your own party instead, you don't suffer any penalties from it, and deny the boss from dropping your morale for those units. Basically, he's killing everyone so they don't get demoralized, as weird as it sounds.

For Shadow Lord specifically and why he's required, he's the only unit I found with 3 guaranteed staggered guts (granted, I didn't look too hard). I'll explain this in the next section, but its important for the 0-AI breakage issue. It's also should be noted that he imperils dark (a weak element of the boss), and can break DEF for his BS chaining move, for good role compression here.

I never tested Phase 2 (ie: super-murder turn), so please do not use an LB ever (barring the safe turns). I don't want to think too hard on the AI breakage potential for that.

PS: If your wondering why my clear pic took so long, due to forgetfulness, both Lara & Shadow Lord were geared less than stellar, to say it nicely. On the bright side, I got to test a long format clear for some heavier testing for possible AI breakage for this clear.

AI Breakage explanation

At this point, you can dive out now; it's going to be technical AI stuff which isn't particularly important to how to cheese the boss.

Before going into it, this boss has a fairly complicated and nicely laid out AI (from a code perspective). However, no boss has been realistically designed for entire teams either hiding/dying for multiple turns, nor should ever really be expected to. It's the combination of this and the complicated AI (and maybe speghetti code too) that leads to the boss doing weird things that honestly not fully well understood.

First, Phase 1:Turn 3 does not like hide cheese strats. From testing, if the boss doesn't get to do his normal actions for this turn due to strat, then the boss will stay longer in the turn for some unknown number of turns (maybe ~5-ish from some minimal testing). Ontop of it, the number of storms (Chromatic/Polar/Magnetic) it does for this turn will also fluctuate beyond the normal 5. If that wasn't enough confusion, the storm fluctuation also can carry over to future 1:3 turns. Why this occurs is not fully understood, and honestly, I don't expect it to ever be fully understood from a partial blackbox testing/probing scenario. This is why in Alkatrev's video has him seeing ~2 storms on a 1:3 turn that was extended by an additional 2 turns (at least pre-threshold from other testing/attempts done)

Second, in order to advance out of 1:3, all remaining storms must be used on living and non-hiding party members. I suspect this oddity has something to do with the "wait()" command in the AI, but cannot confirm either way. For something like Alk's strat, living thru the 2 remaining storms (due to the count flucation above) is fine. But for a full 5 storms, you will need either some serious tanking breaking, or several staggered guts.

Both of these together lead to some potential problems, especially after crossing a threshold. From several clear attempts using alk's cheese strat, this has occassionally lead to weird disjointing that causes the first paragraph issue to no longer follow the expected rotation w/ the reduced storm counts, followed by the second paragraph issue of living thru all the storms. It also appears this happens at random for some reason. It might be due to the turn of the crossing messing with the internal counters, or some inherent randomness in the AI breakage.

Hence, why this 3T rotation was created. The first issue is prevented by never skip-hiding 1:3 mechanics, so the AI breakage should never appear. The second part is fixed by having an unit that can live to see all 5 storms: Shadow Lord w/ his 3 staggered guts. A substitute would probably be an unit w/ 2-stage guts with an equip to give a third, but Shadow Lord is fairly role compact for this strat seeing that we are losing 3 party slots to hiders.

Conclusion

Wave, wave, wave, wave, wave (dead)

Edit: Adding in Flip's clear video for a non-text variant.