Zeromus ( Final Fantasy IV boss ) Zeromus is the final boss of " Final Fantasy IV " and the spirit and hatred of Zemus incarnate . Zeromus appears with three battle scripts , with only the third being possible to defeat . The party faces him in the Moon . After Fusoya and Golbez defeat Zemus , Zeromus emerges from his corpse , proclaiming itself as Zemus ' s hatred . Fusoya and Golbez ' s attacks have no effect on Zeromus , and when Golbez tries to use the Crystal , the creature proclaims evil hearts cannot wield it , and attacks both with Meteor . Everyone left at Mysidia prays for Cecil . Their prayers revive him and his party , and Golbez hands over the Crystal and beckons Cecil to use it . He does so , and Zeromus ' s invincibility disappears , revealing its true form . In some versions , Zeromus is susceptible to the second form glitch . Battle . 2D versions . Once Cecil uses the Crystal , given by Golbez , Zeromus becomes corporeal and the true battle begins . In the SNES , PS , GBA and PSP versions , Zeromus has considerable prowess in magic ; his signature moves include Big Bang , a powerful magic attack that deals around 1 , 900 - 2 , 600 damage to each party member and inflicts Sap . His Black Hole attack nullifies the party ' s magical benefits ( it does not affect Zeromus himself ) , as well as a variety of other offensive magic . Strategy . Zeromus appears in a non - corporeal form at the start of the fight , and will not attack and cannot be damaged . This is a good time to cast beneficial status effects . After Cecil uses the Crystal , Zeromus starts off with Big Bang . Rosa should use Curaja and revive any KO ' d party members . Cecil should attack or , alternatively , use Elixirs , while Kain jumps . Rydia can use her summons , preferably Bahamut . Black Magic and Holy should be avoided , as they will be countered by Flare . Edge can attack or throw Fuma Shuriken s or other powerful weapons , as they will not be needed when the battle is done . When Zeromus begins to shake , it means he is about to perform Big Bang . Rosa should keep steady with the healing while the others unleash what they have against the boss . 3D versions . In the DS , mobile and Steam versions , Zeromus will counterattack Rydia ' s summons with Osmose , and Black Magic and Holy with Flare . Zeromus will shake when he gets a turn , dispelling all status effects on the party . A Dark Matter can be stolen from Zeromus . It can be used to fight the superboss Proto - Babil . Strategy . Using summons prompts Zeromus to counterattack with Osmose , but this can be exploited ; if used at the right time , Rydia ' s summon will cause a slight delay and counter with Osmose . However , this will not prevent Zeromus from using Big Bang immediately after . Rosa should heal while the others concentrate in using their best attacks . AI script . 2D . " Disrupt " ( SNES translation ) is indicated by Zeromus shaking . Zeromus absorbs Flare , presumably to halt what would otherwise be the most efficient method of dealing magical damage . If Zeromus has a turn while he is between 16 , 000 - 12 , 000 HP and in phase 2 , he will refill his health to the max ( this action is invisible to the player ) and switch to phase 3 . He will not do this if the party knocks his health below 12 , 000 HP before he can heal himself , thereby leaving him in phase 2 . 3D . If HP = > 90 , 001 If HP is between 30 , 001 and 90 , 000 If HP < = 30 , 000 At all times : " Disrupt " ( SNES translation ) is indicated by Zeromus shaking . Zeromus absorbs Flare , presumably to halt what would otherwise be the most efficient method of dealing magical damage . Zeromus counters Black Magic with Flare , White Magic with Whirl , and summons with a multi - target Bio . Musical themes . " Zeromus " ( originally " Saigo no tatakai " , " The Final Battle " ) plays during the final battle . It was rearranged and included in the Black Mages ' second studio album " " .