How to access:
Clear all of the Event stages (except the Co-Op LV 150 stage, which is optional). This will give you access to the CHAOS stage.
Stage Difficulty: Level 180 (CHAOS)
Mission Requirements:
Score 470k |Clear without any KOs | Clear within 100 turns | Take 10000 or less HP damage
Boosted Characters: Lenna, Seifer, Ace, Faris, Relm, Fang
Many team ideas with and without boosted characters are available in this event’s Call to Arms!
Fight Overview
This fight shows signs of the next powercreep wave coming to DFFOO. The damage per turn requirement to complete the fight within the maximum turn count is tuned with the most recent damage dealers in mind, especially if you waste time dealing with the boss’ debuffs or allow it to get more than one Curaga off. The bosses use a mix of Melee and Magic attacks, with the only elemental damage coming from Jecht’s 
attacks; and neither has special resistances to any weapon types.
Recommended:
Strong single target or group damage dealers, especially those with free turns;
Characters with the ability to delay enemies or to manipulate turns to act more often;
Characters with abilities triggered by enemy actions, like traps or counterattacks;
Debuff avoiders like Lenna, Selphie, or Ignis (debuff cleansing is not as useful since the worst debuffs are short duration);
If no debuff avoidance, characters who apply a large number of buffs can help get rid of the debuffs;
Healers to deal with the unavoidable HP damage from the Keeper’s recast ability;
Debuffers work very well, especially if you have Poison or Sap to keep Jech’ts BRV low;
Dispellers are not necessary, but help removing their annoying buffs;
Tanks are great to make the run safer, but watch out for the guaranteed hits and guaranteed breaks explained in the last section.
Avoid:
Characters who deal , 
or 
damage, due to the elemental absorption, unless you focus their elemental attacks on Jecht only;
Jack, Edge and other characters who rely on evading attacks, if you don’t want to worry about the guaranteed hits from the Keeper.
Summon options: Leviathan, Brothers and Diabolos are good summon options (choose the one appropriate to your team). The constant HP damage through the fight will easily trigger the passives for Leviathan and Diabolos, but might also cause you to lose the benefit of The Brothers. Shiva, Ifrit and Alexander are not recommended due to the elemental absorption.
Wave 1: Sanctuary Keeper and Jecht Manikin
| BRV Attack |    attack |
| Gore |  attack; |
| Tail Sweep | attack; inflicts  5T Poison, 5T Sap on target |
| Mana Breath |   attack; inflicts  3T DEF Down on all targets |
| Curaga | Restores own HP; grants  5T HP Regen to self |
| Verse Shot | attack; inflicts unavoidable Break on target (ignores evasion); “+” version: also increases BRV, and under 50% HP, adds a follow-up action (usually Tail Sweep or Curaga) |
Photon Wings | Recast ability; recovers from Break; guaranteed hit (ignores evasion); reduces all enemies BRV based on target’s MAX HP (but never Breaks, only reduces BRV to 0); increases BRV by targets’ reduced BRV; attack;increases BRV by HP damage dealt; inflicts 2T Stop (freezes EX recharge gauge bar), 1T Blind on all targets |
Power increased…!: Raises ATK, DEF, SPD, INT BRV, MAX BRV (activates at 80% HP)
Power further increased…!: Raises ATK, DEF, SPD, INT BRV, MAX BRV (activates at 50% HP)
Enrage: No. They do not power up when one is defeated.
| BRV Attack | attack |
| HP Attack | attack; |
| Beast Rush | attack; grants  ATK BRV Up to self;high turn rate |
| Beast Rush+ | attack + attack; grants ATK BRV Up to self;high turn rate; activated if BRV is at least 30% of max before the attack |
| Jecht Slash | attack + attack; grants MAX BRV Up, PHYS ATK Up to self;high turn rate |
| Jecht Slash+ | attack + attack; followed by another attack + attack;grants MAX BRV Up, PHYS ATK Up to self;high turn rate; activated if BRV is at least 30% of max before the attack |
Does NOT gain any stats increases at 80% HP and 50% HP.
Enrage: No. And the Manikin is NOT revived by the Keeper.
This is a pretty straightforward fight, with only a single wave and two enemies, but you have to understand and respect them to avoid some traps.
First of all, the Jecht Manikin is only an accessory. As you can see from the detailed stats above, his move list is very simple and he does not gain any stats increases based on HP lost. He will not be revived by the Keeper either, so if your team is not reliant on group damage, rushing Jecht down first is a very viable option. Jecht will keep rotating between his Beast Rush and Jecht Slash moves, tending to use regular BRV attacks when broken. The only real threat is if you allow Jecht to begin his turn with enough BRV to activate his Jecht Slash+ skill. In that case, he has a very high chance of insta-killing a character, even if they have a Last Stand passive (since it will be two separate HP attacks).
Now for the real threat. The Sanctuary keeper has a very nasty recast ability, Photon Wings: it is a guaranteed hit that ignores evasion, drains a large amount of BRV from your team and deals unavoidable HP damage; it also inflicts 2T Stop (freezes EX recharge gauge bar) and 1T Blind on your team. The Stop debuff can really hinder characters who rely on their EX for free skill uses, like Lightning, Rosa, Leo and Selphie. And Blind, well, hinders everyone, especially characters like Emperor and Vanille, whose traps also have a miss chance if they activate while the debuff is in effect. Remember that you can use an AA as a free turn to get rid of the 1T Blind, in case you absolutely can’t afford to miss the next attack.
This attack is the main reason for debuff evasion to be highly recommended in this fight. The HP damage it deals is also significant, and can overwhelm your team over time if you don’t bring enough healing. The only saving grace is that this attack will never Break your team, at most reducing their BRV to 0. If you bring Jack, be very careful to not use his EX when the Keeper’s recast bar is full.
The rest of its arsenal complements Photon Wings. If you see an attack while the recast bar is not full, it will be a Mana Breath; it will attempt to break your whole team while also reducing your defense, and if it does cause a break, it will fill the Recast bar by a lot. Its other annoying attack is Verse Shot, which causes an unavoidable break on the target (ignoring evasion). This break can screw your turn order and instantly remove Zack’s shields; worse yet, when the boss is under 50% HP, Verse Shot+ will be followed by a bonus attack in the same action, usually Tail Sweep or Curaga.
Speaking of Curaga, that is the other main hurdle of the fight. When hitting 50% HP, the Keeper will counterattack with a Curaga to heal 350000 HP and gain an HP Regen buff for 5 turns. This healing cannot be prevented in any way, but the buff can be dispelled. The bad news is that after that point, the boss can use Curaga again after the buff expires or is dispelled, healing another big chunk of life. With the tight turn count for this fight, allowing the boss to use Curaga more than twice will make it very difficult to Complete the fight. Thus the most recommended strategy to avoid that is to bring a delayer (either in your team or one of the plentiful Leo friends) to keep the boss from acting after it is under 50% HP; then use your summons and all your skills to try and burn it down as fast as possible. Note that using a delayer is more effective if Jecht is already dead, since it will gain your team more turns to act instead of having the boss’s turn “leap over” future Jecht turns.
The “Cheese” Option:
Did we say “annoying debuffs”? And the boss is not immune to its own petard? You guessed it, Yuffie can be used to throw them back and even the odds a bit. Stop will freeze the Keeper’s recast bar for 7 turns, saving you the trouble of dealing with his worst move for a longe time; and Blind for 6 turns makes both enemies much less dangerous. However, unlike fights with MAX HP Down debuffs, it is not an automatic win. You still have to deal with the instant heal from Curaga if you let the boss act freely after it is used the first time, so the delay strategy is still essential. This video by Inkwelder shows the Yuffie strat in action: