Lady Yunalesca

Lady Yunalesca is the guardian of Zanarkand and a villainess 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.