Lady Yunalesca

Lady Yunalesca is the guardian of Zanarkand in Final Fantasy X. She was the first summoner to defeat Sin long ago, as well as the daughter of Yu Yevon, and now exists as a spirit involved in obtaining the Final Aeon for future summoners, requiring one of their "guardians" to be sacrificed to become the Fayth for the final summoning. Yunalesca actually sacrificed her own husband in her case.

Prior to the game, Lord Braska went to Zanarkand and sacrificed Tidus' father Jecht to be the Final Aeon, but Auron protested against this practice and went back to complain to Yunalesca, and was told that Sin is always supposed to come back and their journey is ultimately pointless. Auron then attacked Yunalesca, but was "killed" by her.

When the player's party arrives at Yunalesca's temple in Zanarkand, Lord Braska's daughter Yuna (who is actually named after Yunalesca) realizes that her pilgrimage is futile, and they see a vision of Auron fighting Yunalesca. Yunalesca says that the true purpose of "destroying" Sin is merely to give the people of Spira "hope" to carry on in spite of Sin's continued presence, and then attacks when Yuna refuses to go through with the ritual.

Lady Yunalesca at first fights in her beautiful humanoid form, but then reveals a giant Medusa monster attacked to her body. After a long and difficult battle, she is defeated and destroyed. She returns in Final Fantasy X-2 however as a guardian in the Via Infinito dungeon, where she takes the form of a giant basilisk called "Chac". After being defeated here, Yunalesca is finally put to rest.