Final Fantasy XIII

"Exorcist"

You must complete mark missions: 7, 12, 27, 30, 34, 51, 64 (the 7 undying marks).

Only missions 51 and 64 should give you any difficulty if you haven't power leveled your characters yet, the rest I was able to beat pretty much immediately after finishing the story.

For mission 51 (Attacus), you need to finish all 16 of the Faultwarrens mark missions (missions 35-50), which takes 6 run throughs of the Faultwarrens to complete A1-E6 on the Faultwarrens chart. After completing all of them, you can make one more run through and all of the D island (D1-D4) will have a new Cie'th stone that will take you to E7 where you can fight Attacus. Attacus cannot be staggered and is susceptible to Deprotect, Deshell, Slow and Curse. The key the this battle is having a Sentinel in your party. Twice throughout the battle Attacus will upgrade his sword to a more powerfull one and has the ability to kill someone in your squad with 1 blow if they are not a Sentinel and provoking him. This attack follows his "Concentrate" warning, letting you know when you need to make the switch to the paradigm with the Sentinel. Other than that, do the usual Com/Rav/Rav to get this chain gauge up and hurt him and he will go down eventually.

For mission 64 (Vercingetorix), I used Light/Fang/Hope. My paradigms were:
Sab/Sab/Sab
Sab/Sen/Med (default)
Med/Sen/Med
Sen/Sen/Sen
Syn/Syn/Syn
Med/Med/Med (never had to use, but good to have just in case)
Use Fortisol and Aegisol before going into battle. To start out I would cast Poison on the enemy and then switch to Combat Clinic (Med/Sen/Med) and just heal until he went into his invincible Impenetrable Auro ability. This is where you take the time to heal up if you need it and replenish your buffs with the Syn/Syn/Syn if you lost any during his Putrescence attacks. Then I switch to Sab/Sab/Sab and cast poison while the other 2 party members use Dispel to remove the buffs he gave himself, if the poison worked I switch to Med/Sen/Med and repeat everything I just explained, if not then switch to Sab/Sen/Med and cast poison until it hits then go to Med/Sen/Med and repeat. Somewhere around his 50% point, he will start using his Wicked Whirl attack that can wipe out your entire party. The second you see this, switch to your Sen/Sen/Sen paradigm and back to Med/Sen/Med after it hits to heal up. Do this and the Poison attacks should kill him in ~10 minutes!

For Mark 64, I used a slightly different approach. Maxoplata's method is probably the safest method I've read about as you always have a healer present to top your hp off. However (and correct me if I'm wrong), I don't know if it will get you a 5-star rating in the battle. I also used Lightning, Hope, and Fang and my paradigm deck looked like this:

COM+RAV+RAV
COM+RAV+MED
SAB+SAB+SAB (default)
SYN+SYN+SYN
MED+MED+MED
SEN+SEN+SEN

Use Aegisol and Fortisol before the fight and begin by debuffing him. Maxoplata is also absolutely correct that you want to have poison working at all times. In order to speed up his death, I also tried to keep Deshell, Deprotect, Imperil, and Slow on him. Once he's debuffed top off your hp with MED+MED+MED if you need to and lay into him with relentless assault.

Early in the fight you may not get much of a chance to hit him with this paradigm before he goes into Impenetrable Aura but thats okay. As soon as he does, heal with MED+MED+MED, refresh buffs with SYN+SYN+SYN, and finally switch to SAB+SAB+SAB to be ready to dispell his status enhancements and debuff him with the spells mentioned above. Finally switch to Relentless Assault again and continue doing damage. The Diversity (COM+RAV+MED) paradigm is in there in case you need just a small amount of healing during your dps phase.

Finally, the SEN+SEN+SEN paradigm is to be switched to as soon as you see Wicked Whirl to minimize the massive damage. After it's over, immediately switch to Salvation (MED+MED+MED) to heal up and continue dpsing him.

During the later stages of the fight, his healing during Impenetrable Aura is quite significant (1 million or more hp total) and he also hits a lot harder. The key in the late stages of the fight is to do damage faster than he gets it back. To this end, I began the fight with at least 4 TP segments so that I could use Refresh twice. Using this technique is a lot quicker than switching to a healing paradigm and missing out on damage that you could be dealing to the mob.

Using this method, I finally managed to beat him on my third attempt (largely because of stupid healing mistakes on the first 2) in 8 minutes and got 5 stars.

In order to get the Exorcist achievement, you must defeat the seven undying marks in missions 7, 12, 27, 30, 34, 51, and 64. The last undying mark, Vercingetorix in mission 64, does not become available until after beating Barthandelus in Oerba. The player can advance immediately to Chapter 12 upon beating beating Barthandelus and the game is structured to greatly discourage a high level confrontation with Vercingetorix until post-game activity. However, this guide demonstrates how the Exorcist achievement can be unlocked by beating Vercingetorix before leaving Chapter 11.

The first six missions required for the achievement are fairly straightforward. In fact, if any of 7, 12, 27, 30, 34, and/or 51 give you difficulty, it is most likely because you need to level up your characters and equipment to the maximum extent possible considering the limitations of remaining in chapter 11.

Vercingetorix in mission 64 is one of the two most difficult fights of the game (the other is Long Gui). None of the other bosses compare in difficulty to these two. During post-game play, it is possible to beat and five-star this battle using a defensive strategy where most of the damage is inflicted by poison. However, in chapter 11, the party’s defenses are not strong enough to withstand multiple Wicked Whirl attacks in Vercingetorix’s final and most powerful form even in a Sen, Sen, Sen paradigm.

A chapter 11 strategy (that will also work well in post-game play) uses Snow as the leader. Snow has about 12K HP after the post-Barthandelus Chrystarium upgrade is maxed out. Lightning, Vanilla, and Hope each have less than 10K. All characters should be maxed both in the Chrystarium itself as well as in points.

Adamantoises/tortoises can provide platinum and trapezohedrons (to upgrade weapons to tier 3). Adamenchelid's provide gold dust and Scarletites. Once you’ve done enough farming you should be able to end up with three diamond bangles--two from pickups and one from a platinum bangle upgrade (Scarletite). Create the following party:

Snow Light Van
Syn Med Syn
Sab Sab Sab
Sen Sen Sab
Sen Rav Rav
Sen Med Med
Sen Sen Sen

Snow: Diamond bangle X 3
Lt: Nimble Boot, Aur Sash, Sprint Shoes
Van: Aurora Sash, Nimble Boots, Weirding Glyph
Weapons: Wild Bear Lv 1 (Defense), Enkindler Lv 2 (Speed), Nirvana (from Marlboro Wand Lv 3 (Debuff)

You should also have 99 potions and quite a few phoenix downs.

The battle is in two phases. The first is when Vercingetorix has one or two wings a side. The second is when it has three or four wings a side.

It makes it a little easier to start with Aegisol and Fortisol. I stopped using them because they're long gone before you enter the second phase. So, using them creates bad habits.

The first time you encounter Vercingetorix, immediately select item and then librascope to get enemy info. The AI will recognize that Vercingetorix is vulnerable to poison.

The first phase is all out offense. Start with SabX3 and have Snow cast slow. You can use auto because that's his only effective debuff and the AI will select it automatically.
Lightning and Vanilla both have aurora slash first strikes and fast ATB charges. As soon as both poison and slow stick switch to Sen Rav Rav. Keeping in synch with the game mechanics for optimal ATB charge, switch back and forth between Sen Rav Rav and Sab Sab Sab.

The first Impenetrable Aura comes very quickly. Impenetrable Aura is a defensive shell which makes Vercingetorix invulnerable to damage, clears him of status ailments, and zeroes his chain gauge. The good news is that he does not attack while in his aura. Switch to Syn, Med, Syn and force Snow to cast haste on all Snow and Van. Lightning has auto haste so she can wait.

If everything works perfectly, the first impenetrable aura comes as the mark sprouts its second pair of wings. If the debuffs and attacks are not as optimal, the second round will be very short. The second pair of wings will sprout and the sprouting of the wings creates the impenetrable aura.

If you have to go more than two rounds with one pair of wings, it's best to restart and hope the game's AI gives you better attacks.

With two wings, things are more intense. Go down the paradigms in sequence. Make sure all three characters have haste. That's Snows only responsibility in the Syn, Med, Syn paradigm. Vanilla, who can't cast haste provides some very powerful buffs. None of the buffs will last long, though. The goal is to move to Sab Sab Sab just before the mark comes out of his trance and switch immediately to Sen Sen Sab. Once you've got the game mechanics timing down, you can switch as Snow is still casting Slow. If you switch right about the third cast, Snow will cast the remaining two ATB segments as he goes into the paradigm shift. Generally, Slow sticks about 80% of the time or better.

Unfortunately, even super Vanilla with Nirvana and a weirding glyph can get poison to stick less than 20% of the time. The role of the Sen Sen Sab paradigm is to stick poison. I use three potions while waiting for poison. This allows Lightning to provoke the mark and then elude it. She is very good at this with Nimble boots. As soon as poison sticks switch to Sen Rav Rav. Immediately force Snow to challenge to get the marks attention and cancel out using only one or two ATB segments. Then allow the AI to choose Mediguard.

The Sen Rav Rav is the key to phase one. The higher the stagger gauge is the more effective poison is. If I adopted a more defensive posture, even when I outlasted the mark, I was not able to five star it. The first time I beat him I used a defensive poison only approach and got a zero star rating. I took it though because it gave me the gold watch as a drop and eliminated the need to use the Librascope. I then took this more aggressive approach with Sen Rav Rav to five star it with the help of the gold watch bonus.

The good news is the mark is fairly easy to stagger especially if you're fortunate to retain haste on either Vanille or Lightning or preferably both. Even without haste, Lightning's 20% ATB charge and Vanille's 10% faster ATB charge along with a sixth ATB segment drive up the stagger gauge quickly. If you've mastered synching with the game mechanics, you can switch between Sen Rav Rav and Sen Med Med without reducing your ravager attack opportunities.

In phase I, Lightning and Vanilla should not be KO'd. It's not a big deal--that's what the Phoenix Downs are for. I tried Royal Crowns, General Belts, Witches Bracelets, and Diamond Bangles to make them more robust to no avail. They're just not sturdy enough to start out with. Except for the bangles, the other accessories increase defense or resistance by a percentage. In chapter 11, the base is not high enough for them to do much good. I found that to be the case even with Snow which is why I opted for three diamond bangles for him. With the three diamond bangles, he ended up with 15K points.

If a party member is KO'd apply a phoenix down immediately and then switch paradigms. The resurrected ally must first recharge the ATB gauge before engaging. If you're off sequence, switch to Sen Sen Sen, apply Phoenix Down, and then switch to your paradigm of choice most likely Sen Med Med.

If you stagger the mark and you should, the third pair of wings sprouts before long. Again, the sprouting of the wings forces impenetrable aura so there will be at least a brief respite. If the switches between Sen Rav Rav and Sen Med Med have gone smoothly, your HP should be in the green. Again, start with the first paradigm and make sure that haste is on all members. As before, switch to Sab Sab Sab while the mark is still in its trance and execute as he comes out. As before, switch to Sen Sen Sab to inflict poison. Hopefully, you still have haste and Snow will have got slow to stick. Be prepared at any time to switch to Sen Sen Sen if you see Wicked Whirl. Once poison sticks, switch to Sen Med Med.

Sen Med Med is the key to phase 2. It's important to keep Snow in the green and the other two members out of the red. When you have an opportunity do a quick Sen Rav Rav. The timing is important. A typical ravager raid goes as follows:

You should have spent more than a cycle in Sen Med Med so the next paradigm shift will start out fully charged. Switch to Sen Rav Rav a slight pause after the mark announces an attack other than Wicked Whirl. Auto protect (AI will choose Mediguard because you should still have the mark's attention) and watch Lightning. As she begins her third attack switch to Sen Sen Sen and immediately start using potions. While you with Snow as the leaders are using potions, the remaining two characters will try to provoke the mark. Lightning will provoke and elude faster and attract the mark's attention before Vanilla. Once you have used three potions, you can switch to Sen Med Med with fully charged ATBs for immediate recuperation.

Of course, if you ever see Wicked Whirl, you must go to Sen Sen Sen. If you have been successful keeping HPs up, all party member should survive. Use a couple of potions and switch to Sen Med Med with fully recharged ATBs for immediate recuperation.

If a party member is KO'd during Wicked Whirl while you are in Sen Sen Sen, use a Phoenix Down (or two if both Vanille and Lightning are KO'd). When you switch to the next paradigm, resurrected member ATB gauges will be fully charged.

It's best to try to survive two rounds with three pairs of wings and make your move on the third round. Stick the mark with slow and poison using the strategy and go to Sen Med Med. Get ready for a ravager strike. The circumstances should be right. All members should have fairly good HPs, you should have been in Sen Med Med over a full cycle, and you should paradigm shift a half pause after a non-Wicked Whirl attack is announced. Auto protect. As Lightning goes into her third attack, switch to Sen Sen Sen. Execute the stopga technique and switch back to Sen Rav Rav. Wait until the attack is fully executed--Lighting and Vanilla are faster than the mark--then switch back to Sen Sen Sen and execute stopga again. Return to Sen Rav Rav and stay there until the mark goes into Impenetrable aura.

As you might surmise, a lot can go wrong. There is no guarantee of victory in a chapter 11 battle. When it goes right, this is what happens. The first Stopga prevents the mark from executing Wicked Whirl. The second Sen Rav Rav attack would normally result in the sprouting of the fourth pair of wings and the mark going into Impenetrable Aura. However, my conclusion is the mark needs a fully charged ATB bar to do that and you hit the mark with the second stopga and the third Sen Rav Rav attack. That third attack should stagger it and I've staggered it as early as the second attack depending on how successful the debufs have been raising the stagger gauge.

The goal is to reduce the life gauge of the mark before it sprouts the fourth pair of wings.

The end game can be played one of two ways--with an Eidolon and without. If the mark has a very short green bar when it comes out of impenetrable aura, stick slow on it with Rav Rav Rav and poison with Sen Sen Rav. Stay on your toes for Wicked Whirl. Once poison sticks, call the Eidolon. Reinforce slow then go to Sen Rav Rav. The mark now spends a lot of time between Auras so once the Eidolon leaves you can hit it with the ravagers then retreat to Sen Sen Sen until the poison kills it.

If the mark has a longer green bar, it's best not to call the Eidolon but use your 3 remaining stopgas to execute the previous strategy. It's tougher to execute than the Eidolon approach but more effective. The main difficulty is it’s hard to keep the HPs of your party up. As a result, you incur more risk. From Sen Med Med go to Sen Rav Rav. Execute the attack, retreat to Sen Sen Sen and execute stopga. Hit the mark with another Sen Rav Rav retreat to Sen Sen Sen execute stopga. Then hit the mark with a final Sen Rav Rav attack and retreat to Sen Sen Sen use potions like crazy and wait for the mark to die.

If you execute right and the mark does not start out with Wicked Whirl, you should never see Wicked Whirl with four wings. It is extremely difficult to survive a four wing Wicked Whirl even in Sen Sen Sen with HPs of all members in the green. Snow can survive. Vanilla and Lightning cannot. If you're fast and fortunate, you can revive the fallen members and recuperate.

More likely, you're behind the power curve. The best approach is to revive one member switch to Sen Med Med, revive the other while the first heals, execute stopga and retreat to Sen Sen Sen to regroup. I have survived using this strategy and won. However, more often than not Vercingetorix gets the upper hand and defeats me. What helps is that this activity generates an extra TP segment so you can execute stopga an extra time. That extra stopga may be enough to snatch victory from the jaws of defeat.

This advanced battle at a low level is super intense gaming. Final Fantasy XIII has a spectacular battle system. Unfortunately, the game tries to spoon feed the player and avoids difficult challenges. A chapter 11 mission 64 is white knuckle gaming and showcases the battle system admirably. It is not easy. It took me almost a week playing hours every day on this one battle before I could beat it and another day to five-star it. The mark drops the gold watch that considerably improves your battle score. So, it’s not too difficult to progress from zero to five stars.

The gold watch extends battle target times by 10%. In this case, 10% is a significant amount because of the long battle time to begin with. It should be enough to result in a five-star victory when equipped. The best slot is to replace Vanille's Weirding Glyph with the Gold watch. For the party to get the gold watch bonus, Vanille must be alive at the end of the battle.

You do not have to five star this battle to unlock the Exorcist achievement but you do in order to earn the gold L'Cie Paragon achievement that requires you to five-star all missions including this one. So, you might as well bite the bullet here while your attack sequences and timing are committed to muscle memory.

This achievement, whether unlocked during chapter 11 or during post-game play is challenging. Congratulations.

On Mission 64, I followed this video and 5-starred it in my very first try, so enjoy it.

The video is not mine, and all credits go to MasterLL.