Sinspawn Gui is the result of the Sinspawn gathered for Operation Mi'ihen fusing into a monster that breaks out of its cage and fights the party in Final Fantasy X, just as Sin approaches the shore. The party is scattered by Sin's attack, and Seymour Guado grapples with the reanimated body of Sinspawn Gui alone until he is joined by Yuna and Auron; both encounters count as one boss.
Sinspawn Gui is the result of the Sinspawn gathered for Operation Mi'ihen fusing into a monster that breaks out of its cage and fights the party in Final Fantasy X, just as Sin approaches the shore. The party is scattered by Sin's attack, and Seymour Guado grapples with the reanimated body of Sinspawn Gui alone until he is joined by Yuna and Auron; both encounters count as one boss.