The Fayth are the souls of people who gave up their lives willingly to protect the people they love, then began their transformation into aeons and who knows how many people gave up their lives before zanarkand was destroyed and who knows how many temples are left undiscovered 0_o

Well maybe the person who became bahamut was from zanarkand and later his body was taken and placed in the temple of Bevelle by High priests or something...my opinion anyway.You know that we Yevonites are very secretive(cough)Only to protect the people I ensure you.

well Bahamut's fayth was in Dream Zanarkand watching over Tidus, and I think that he was from Zanarkand. This way the fayth could be in the city but yet know that he helped create it. AND I think that bahamut's fayth was also part of the reason he went to Spira. The fayth helped bring Sin in between each other. And after dream Zanarkand was destroyed you were actually inside Sin where you fought BFA. So dream Zanarkand is actually inside Sin and the fayth just dream Sin and Yu Yevon dreams Zanarkand so that way he/she can live in zanarkand without having to worry about the war again, and the reason the Yu Yevon takes the form of the Final Aeon is to create a new sin and yet create a new Zanarkand. A calm lasts for 10 years and it was 10 years in between Jecht's and Tidus' disappearence, so every ten years when Sin is reincarnated and then destroyed Sin is allowed to go into itself and pull out someone. that way Sin will be reincarnated. and then the person that was pulled out becomes a summoner's guardian only to be the Final Aeon which Yu Yevon takes over only to make another Dream Zanarkand, then therefore the "Spiral of Death" as Seymour puts it.