Attacus Attacus is a mark in " Final Fantasy XIII " . One of the nine Undying , it is accessed via a third Cie ' th Stone in the D stages after every stage of the fal ' Cie Titan has been cleared in the Faultwarrens . Attacus is fought in " Mission 51 " . Titan creates a Behemoth King for the final task , but Attacus appears and slays the Behemoth King , afterward turning on the party . Battle . There are three phases to Attacus , with the second and third phases marked by the abilities Unrelenting Blade and Peerless Blade respectively . Whenever Attacus uses a special skill , he will attempt to clear all of his debuffs and debuff the party with Deprotect and Deshell . All of Attacus ' s attacks randomly inflict Slow . When Attacus uses Unrelenting Blade he becomes stronger . Attacus gains strength whenever he moves to a new battle phase . Attacus is immune to and , although it can be stagger ed at 999 % and also can be launched when staggered , driving up the chain all the way to 999 will likely take too long , as the 20 minute time limit must be kept in mind , as if the battle takes over 20 minutes Attacus will cast Doom on the party leader . Strategy . The fight can be surprisingly easy with Fang , Lightning , and Snow with Fang as the party leader . It is recommended to get Stage 10 Crystarium for Lv . 5 Sentinel on Snow . Using Fortisol and Aegisol is not mandatory , but would make the beginning of the fight easier before switching over to any one of the paradigm s with Snow as the Sentinel . It is advisable to start out with SAB / RAV / RAV , casting Deprotect and Slow . Slow is more important than Deprotect as it increases the time between Attacus ' s special attacks . Once Attacus is afflicted with the two debuffs , the player should switch to SYN / RAV / RAV for Bravera . Only Lightning and Fang need it . The player should then switch over to RAV / RAV / SEN and bring the chain gauge up to 300 % ; then switch to COM / COM / SEN . Whenever Attacus uses a special skill and attempts to clear his debuffs , the player can switch over to SAB / COM / SEN and recast Deprotect and Slow , then switch to SYN / COM / SEN to recast Bravera and Haste on Fang and Lightning . When the buffs and debuffs are on , the party should stay in COM / COM / SEN . The party will not have to heal Snow because he ' ll use Mediguard . If neither Fang nor Lightning can survive the initial period when the party is raising the chain gauge before Snow shifts to Sentinel , one can change the paradigms to have Snow as the Sentinel in all of the paradigms . One can also set Lightning as Ravager while Fang is buffing / debuffing instead of Commando to raise the chain gauge even higher . This fight can also be completed relatively easily with Lightning , Fang and Hope , as long as the player has developed Lightning in the Sentinel role to at least the point where she gains the defend ability , Elude . It is not necessary to have developed the characters in roles outside of their initial roles . It is also not necessary to have any level roles , but the increased health obtained from working towards the level 5 boosts is helpful . Once Attacus uses Peerless Blade it becomes necessary to use SEN / SEN / MED whenever he begins using the Meditate attack . With Lightning as leader she shouldn ' t use use Provoke only Elude , and if it hits Lightning or Fang , they should survive easily , and Hope will quickly heal them ; if it hits Hope , the player should switch to MED / SAB / SYN and use Raise ( or Phoenix Down ) , then allow Hope to rebuff himself . If the characters are developed enough , the battle should end before 20 minutes . Summoning an Eidolon also halts the Doom counter . Low Level Strategy . As Attacus gains strength whenever he moves to a new battle phase , the player with a weaker party can end up in an endless loop of healing and defending while not getting many attacks in , prolonging the battle for too long for Attacus to use Doom . In this case , the player can try to raise Attacus ' s chain gauge as high as possible before he powers up his attacks and moves to the next battle stage . The player can use three Ravagers to drive up the gauge . Magic won ' t deal much damage , but will increase the chain . Once Attacus is at around 600 - 700 % chain , the party can resume the attack properly and bring in some Commandos . With a high chain the party can kill Attacus much faster when he is actually powerful . Etymology . Attacus ' s Japanese name is Spartacus .