Final Aeon
From Final Fantasy Wiki
The Final Aeon is the Aeon that a Summoner gains at the end of their pilgrimage to Zanarkand. The Final Aeon is created from someone who shares a deep relationship with the summoner: a friend, family member, or lover. Yunalesca was the first to call the final Aeon, which was her husband, Lord Zaon. The Aeon is only used once, during the final battle with Sin. The Aeon has enough power to be able to pierce Sin's armor. When Sin is defeated, Yu Yevon emerges from his armor and takes control of the final Aeon, severing the mental link with the summoner. Once Yu Yevon merges with the Final Aeon, he turns it on the summoner and kills him/her. Yu Yevon begins using the Aeon to rebuild Sin, and this period of rebirth is known as the Calm.
During the game, the Final Aeon is mentioned frequently as the goal that Yuna is hoping to achieve; however, because of the path the storyline takes, she does not receive her Final Aeon, as she learns of the futility of trying to defeat Sin with the Final Summoning. In the final battle before challenging Yu Yevon, the party meets and fights Braska's Final Aeon, who is really Jecht, the last fayth that Yu Yevon used to create Sin.
