Yunalesca ( boss ) Yunalesca is a storyline boss from " Final Fantasy X " fought in Zanarkand Dome . The battle is fought in three stages , with her becoming more demonic with each change . Her third form resembles the sprite of Goddess from " Final Fantasy VI " . The Sun Crest can be found after defeating Yunalesca , revealed by descending the end set of stairs . In the PAL , " International " and " HD Remaster " versions , if the player does not obtain it upon her defeat , the next opportunity to obtain it is after defeating Dark Bahamut . In the " Final Fantasy X HD Remaster " version , defeating Yunalesca earns the Overcoming the Past trophy . Battle . Yunalesca has three forms , each having a separate HP pool . Whenever a form is defeated Yunalesca will transform into her next form . Yunalesca ' s first form counters physical attacks with Blind , magic spells with Silence and Special commands with Sleep . On her turn she will alternate between a weak physical attack , which removes positive status effects — except Reflect — and Absorb , which inflicts damage equal half of the affected character ' s maximum HP and heals Yunalesca by the same amount . Yunalesca will start the second round by using Hellbiter , which puts the party in Zombie status , and then will cast healing spells , such as Regen and Cura , on the party . She will often counter - attack with a weak physical attack with the same properties as in her first form . Yunalesca will begin the third round with Mega Death , which kills all party members not afflicted with Zombie or protected by Deathproof . Yunalesca retains Hellbiter , Regen and her physical counter - attack from her previous form , but now has access to Curaga which she will use against a party member , and Mind Blast , which attempts to inflict Curse and Confuse on all party members . Yunalesca ' s third form pattern of attacks is : When an aeon is used against Yunalesca in any form , she will cast Absorb on them on every turn . Strategy . The fastest option , assuming one doesn ' t care about everyone getting AP , is to steal four Fire Gems from Flame Flans in the Calm Lands and ensure Rikku can mix Trio of 9999 ( Quartet could work , but it would need to land on someone who has the ability Use ) . When facing Yunalesca , Rikku must mix Trio of 9999 and throw four Fire Gems for a quick win . Before the battle , it is useful to have Yuna and Rikku reach Overdrive , along with any aeons . It is beneficial to customize the ability Auto - Med on either Rikku , Wakka , or Auron . When the battle begins , the trio should be in the starting line - up and steal a Stamina Tablet from Yunalesca . It can be used in mix with a Potion and to get Mega Vitality , which will double everyone ' s hit points . Yuna is handy for Reflect and Esuna . When the second phase starts , the party should continue the same strategy , mixing in Overdrives , although Yuna is needed to Dispel any Regen that might land . Whoever is the Auto - Med can function as a curer and use Holy Waters to cure the Zombie . A good follow up is to have Yuna use Curaga . However , the party must ensure at least one zombified player is on the field in case of Mega Death . Having armor pieces with Death , Zombie and Confuse protection would be optimal , but the player will need to switch armor at the appropriate time by watching Yunalesca ' s attack pattern . To get Farplane Winds needed in customizing the ability Deathproof , the player can capture one of every type of fiend from the Calm Lands for the Monster Arena owner and he will reward the party with 60 Farplane Winds . This is especially useful for Yuna to immunize her to Mega Death even without the Zombie status so she can revive and heal the others . It is also possible to use Auto - Life to survive Mega Death by either casting the spell or by using Rikku ' s Hyper Mighty G . If Yuna has learned Holy , it is a good time to use it . Another tactic for the second and third phases is to keep the Zombie status active for any participating party members and have Yuna bestow them with Reflect . This heals Yunalesca on her succeeding turns but it also helps her refrain from using Mega Death . The party must have good Defense and Magic Defense to minimize damage from Hellbiter . If Yunalesca attempts to put Regen on a zombified party member with a Reflect status active , and it bounces back to her , Yuna can Dispel it . This tactic can work faster if any of the party members have SOS Haste and SOS Protect . Parties without Break Damage Limit can still get an Overkill on Yunalesca by using Bahamut ' s Mega Flare Overdrive , which can exceed 9 , 999 damage .