"A religion started," Rikku said carefully. "It called itself Yevon. Yevon taught Summoners how to perform the Final Summoning. Yevon also had a list of things that people were doing that caused the monster to happen. Using technology. Being at war with each other. Not being self-sacrificing in the name of Yevon. People destroyed their machi-- machines and burned all the books on information. Anything to appease the monster, no matter how irrational it was. They lived in the ruins of advanced cities. And whenever it came back, Summoners would make the long pilgrimage to Zanarkand. Nearly all of them died before they ever got there, no matter how many Guardians they had. If you were a Summoner, it was your sacred duty to get to Zanarkand and die for the rest of Spira, or to go as far as you could and die trying. Yevon called the monster 'Sin.' Subtle, huh?"