Jecht was summoned by magic from a replica of Zanarkand (Zanarkand Dreams), created one thousand years before the events of Final Fantasy X, at that time there's waging a war between Zanarkand and Bevelle. It was started by the leader of Zanarkand, summoner Yevon, which uses the memory of those who live in Zanarkand - fayth. As a result, Jecht and her son, Tidus dreams of the fayth. Yevon also created a malevolent whale shaped creature called "Sin" to protect him, and fayth at the Dream Zanarkand.
Before Final Fantasy X, Jecht was carried into Spira by Sin. It occurs along Final Fantasy X, Jecht and Auron accompanied Lord Braska (Yuna's father). Braska became the tutor and the leader on the road to defeat Sin. Jecht tendency to drink led him into trouble, and left for fear that his family was ashamed of him. Upon arrival in Zanarkand, Jecht gave his life to become the Final Aeon Braska, who defeated sin for 10 years. As the result, he became the new sin. Near the end of the game, which used to immobilize without this weakness. Tidus and his groups finally defeat him and make peace with his father. Yu Yevon is subsequently destroyed, sending Jecht and Tidus to the Farplane, which reconcile.