The stories of High Summoner Yuna lived on for hundreds of years. First, she had been the daughter of High Summoner Braska, and then not only did she become High Summoner herself, but she had defeated Sin for good and ended the need for and lives of the Aeons. Two years after that she became a sphere hunter along with her cousin, Rikku and frien Paine. They were known as the Gullwings. The Gullwings, led by (supposedly) High Summoner Yuna ended up caught in more than just sphere hunting however. The High Summoner still led by a need to save the world had done so yet again by defeating a weapon known as Vegnagun, which had been reawoken after 1000 years of being dormant.
Now however, High Summoner Yuna is long gone. It has been four hundred odd years since Sin was defeated. After Sin and Vegnagun, peace had fallen over Spira for at least two hundred years before the next huge threat came upon Spira. Sin, had been reborn. Millions of people over the years have attacked Sin, in the exact same ways that High Summoner Yuna had done so before them, but each one had failed. It seems that this time, Sin's weakness is something else entirely.
High Summoner Yun managed to defeat Sin for good last time by doing one of a few things. She first entered Sin, by getting inside of him through it's mouth. One thing you cannot do with this Sin, it does not have a mouth.
She then defeated Sin's host, which turned out to be the Legendary Guardian, Jecht, one of Lord Braska's guardians.
She then defeated All of her Aeons, who had been possessed by Yu Yevon, and then she defeated Yu Yevon himself.

"That would be simple! If it were that simple!" Said a small, teenaged, blonde-haired girl. "Who are you telling this story to anyway Riuna? We all know this!" "I know, I know, I'm just trying to figure things out in my own head. It's just easier to do when spoken out loud." The teenage girl looked at me with eyes that could only be that of an Al Bhed's. It's strange that even after thousands of years of existing that there are still pure Al Bhed's left. The girl, Luann, and myself were one of a few that lived here in Besaid. "You're stupid Riuna, what do you need to figure out, we're all going to die anyway, you know." I grabbed a hairtie from my bedside table and put up my long blonde hair into a messy bun. "I might become the next Summoner." Luann stared blankly at me. "Yeah, like I said, stupid. Summoners don't exist anymore, the Fayth have died, the Aeons, gone. Hello, welcome to 400 A.S, (after Sin)!" I frowned. Of course she's right, it was a stupid idea. But I've heard the rumours, Aeons have started appearing again, in all of the temples. It's like they have reawoken, just like Sin, to aid us in our time of need. I tell this to Luann, who only frowns back at me. "Yeah but the temples... no one has stepped in them in almost four hundred years, not even thought about it. High Summoner Yuna told all of Spira that the Vegnagun had basically swallowed the Aeons. Yevonites from all over checked the temples and confirmed their disappearance." Luann went on, but I wasn't convinced. I will go to the temple in Besaid, despite it being a two hour walk away. "I'm going Luann, you can either come with me, or not." Luann sighed deeply, but she stood up, and followed me out of the house.
A couple hundred years ago, water started draining from the oceans, and land began shifting. Before we knew it, Spira had joined up completely into one. There were no need for boats any longer. Besaid is now a massive town, found halfway between Kilika and the once known Besaid Village. Besaid itself could be said to be as big as the thriving metropolis that Zanarkand was 1400 years ago.
It was dark out, but Luann and I could take care of ourselves. We were strong, young independant Al-Bhed women, and fiends barely phased us. But something started nagging at me about an hour into our journey to the old temple. "Luann, we should have had a few run-ins with fiends by now. Why haven't we?" Luann stopped. "You're right, and that's a good question. Maybe something's up? Should we go back?" I pondered for a while. We get lots of fiends just outside Besaid city, but not many people have ventured this far into Besaid woods. "Maybe there are just no fiends out here?" I said and Luann, slightly sceptical, silently agreed, by continuing on.
It had been almost two hours before we arrived at Besaid Temple. The whole area looked like it was from a haunted movie or something. There were trees all around that had fallen to the ground, old huts that had basically disintegrated to almost nothing. The whole area seemed long destroyed, and far from repair. But as we looked at the temple we were shocked to see that it still looks the exact same as it does, from photos three to four hundred years ago. It was untouched. "Riuna, this is kind of creepy..." "Yeah, you're telling me." I swallowed the hard lump that was forming in my throat and I started walking up the steps. "Wait, you're not seriously going in there are you!?" I turned to look at my pale-faced csister. My heart sank a little for her, I was always the more brave. "It's okay Luann, I'm sure there's nothing scary going on here. The temple is probably just protected by a magical force, or somthing. Plus, we walked for so long to get here, we can't turn back now that we're here, right?" Luann squeezed her eyes shut, took in a deep breath, "Right," she said and ascended up the steps with me.
I ran my hands along the white pillars that held up the roof outside the temple. They were slightly cracked, probably from wind damage, but they still stood well-structured and in no danger of collapsing. We walked to the doors and I put my hand on one to open it. I paused, maybe a little longer than I had thought, before placing my other hand on the door and using both hands, and a lot of force, to push the door open.
A soft hum, could be heard throughout the temple. Luann stepped forward. "I've heard this song before..." I walked slowly around the temple, confused slightly by the amount of lighting there was inside. Candles were lit all around. "Hello!?" I called out. Luann shuddered. "Riuna... I think we should leave." I shook my head slowly, "No, we can't. Let's go to the chamber of Fayth." "But Riuna...!" I glared at my twin sister. "You're 19 Luann, for Maester's sake, grow up. There is nothing... to be scared of..." I slowly faltered as I noticed a figure by the entrance door. Luann opened her mouth to talk back at me but before she could get any words out of her mouth she was stopped by the sound of a loud bang. The entrance door had slammed shut. Luann's reaction of course was to scream. I mentally rolled my eyes at her and made my way to the door. I yanked as hard as I could on the handle but it just wouldn't budge. Instantly, I had the urge to scream too, but I supressed it. The hum that could be heard grew louder and then I recognised it... "The Hymn of the Fayth..." Luann stared me dead in the eye. "What are we going to do, are we locked in?" "I think so... we should go to the Chamber of the Fayth anyway, I need to know." I walked on, ignoring Luann's whining. Despite her whining she still followed me up the steps and into the cloister of trials.
Even though the rest of the temple seemed completely intact, the cloister of trials was dark, dimly lit by glyphs on the walls, and it definitely looked untouched for hundreds of years. We made our way through, down steps, and around a corner until we found a small room, lit with candles. At the other end of the room there was an elevator. "I guess the Chamber of the Fayth is down there..." Luann said shakily. Apparently the creepiness of the cloister of trials was effecting her mental state. "Come on, Luann, we're almost there." We walked side by side down the narrow walkway to the elevator. As we both stood on it, it slowly made its way down. At the bottom there was another narrow walkway, and a pair of open doors. We walked inside the Chamber of Fayth and up the stairs to the door to the Fayth. The Hymn of the Fayth was so loud now, that it rang in our ears. I tried to pull open the door, but it wouldn't budge. "How do we open it?" Luann asked, "I have no idea..." I replied and we just stood there for a minute. In my heart, I wished for the door to open, and as if it was responding, the door lifted up and the feathers behind it shifted to make way for us to pass through.
Sure enough, I was right. There, on the ground, was a glass cage of sorts, and in it was a beautifully decorated statue of a bird. Luann was the first of us to speak. "Wow, they said the Aeons disappeared... but, here is one, right in front of us. Pray Riuna! You can become a summoner!" Of course it is what I had intended to do, but the reality of this was surreal, and I had no idea what to do. I was begin to freak out, and almost suggested to turn around and find a way out. But before I had the chance a young girl with brown hair tied in pigtails, and wearing ancient clothes began to float above the Aeon. "Young ladies, which of you shall I bestow upon with my power? Please pray to me and my power will be yours." Luann gasped. I stood there for a moment, taking in this incredible sight. "Please pray to me and my power will be yours." She said again. I wanted to, but fist, I had questions. "Please, if I may, I would like to ask you some questions first?" The young girl showed no expression, and continued floating in mid-air. "I am barely knowledgeable, but I will ask your questions if I can." I was pleased to hear this, so I began to ask. "Why now, after so many years of being gone, have you come back?" I asked hastily. "The purpose of the Fayth is to defeat Sin. When Sin is awoken once again, the Fayth wake from dormancy, ready to be summoned once again." The girl replied. This made sense, sure, if Sin hadn't been defeated four hundred years ago, along with the Aeons, and then the Aeons disappearing for good. "Where did you go? You were gone for hundreds of years." "Vegnagun had consumed us. When he was destroyed, we were too. Not like when Sin had been destroyed. Vegnagun destroyed our remnants, our left-over powers. He destroyed our sleeping souls." This was so confusing, but I had one more question to ask. "Why, after Sin had been destroyed four hundred years ago, is he back now? Or more so, how is Sin back?" The girl shook her head. "This, I do not know the answer to... please, if you have no more questions pray, and I shall give you my power." I was not happy with this last answer, but even though she was expressionless, the Fayth seemed to be getting impatient. So I got down on my knees, and began to pray.
Hours had passed as I prayed. Luann had found the comfiest spot on the ground to sit, then lay, and then she dozed off. It seemed as I prayed I had infinite energy. I was on another plane so to speak. As if my reality were not my own. The Hymn of the Fayth not only rang in my ears, but coursed throughout my entire body. I felt stronger. I also felt as if I were not alone. There were feelings that were not my own. I guess they really meant it when they said that Summoners become one with their Aeons.
A few more hours had passed and I finally began to feel sleepy. I continued to pray however. Before I knew it I prayed one last time and a sudden burst of outside energy shot through me. I fell completely onto the ground and lay there for a while. I don't think I was quite asleep. I could still hear the light snoring coming from my sister, and I felt my heart beating. But I was blissfully still. Euphoric, I suppose. And then, I passed out.
"Riuna..." I heard a voice. Similiar, but out of reach. "Riuna..." The voice grew louder. I searched around for the voice. I was in a dream I guessed, by how unreal it seemed. Where I was, was dimly lit. Blue trees illuminated around me, their leaves were like crystal. "Riuna." A figure appeared before me. It was my sister... "RIUNA!" A slap to my face roused my like nothing before. I sat up so quick I almost fell back again due to a headspin. "Damn girl, you were out cold! I thought you were dead, if not for your loud snoring." I rubbed my face where Luann had slapped me and stood up. I brushed off my dress and looked at my sister. "Well, are you okay? Did it work? Are you a Summoner?" Although I was annoyed at her for slapping me, I grinned at her. "Yeah, I'm a summoner. The first one in four hundred years!" I couldn't contain my excitement. "OHmyGOD! We have to go back to Besaid and tell EVERYONE!" I was about to agree with her, but then a thought hit me. The idea of Summoners now is not one people would believe. "We can't... we have to be discreet about this, until we get to Grand Yevon. We can discuss with the Grand Maester there, he might believe us... until then, we keep quiet." Luann blinked at me, "Yeah but, we need to get into the temples Riuna, how do you suppose we do that, discreetly?" "I don't know, but we'll think of something. Anyway, Let's see if we can get out of this place." Luann was the next grinning. Right, about that. Look up." I did as told, and sure enough, above us was a giant opening. "How on Spira..." "Derr, your Aeon! It flies, remember?" I had heard about the Aeons before, but I couldn't remember which ones could fly.
My Aeon is the Aeon named Valefor. The Bird Aeon. "Right, derr. Alright then." I didn't really think before I started waving my arms around. I felt a strange sensation throughout my body and down through the hole in the roof came a grand bird. As it landed I ran my hand through it's feathers. It was a lot softer than it looked, and even though it looked dangerous, it's eyes were soft and warming. I climbed onto it's back and helped Luann up. Without saying anything the bird knew what to do. We were up, out of the temple within seconds, and we flew high up through the sky. It was daylight. "Take us home girl," I said quietly.
We landed by the entrance to the Besaid Woods, ten minutes away from home. I pet the bird once more and as if it read my mind it flew off. I felt a surge throughout my body, as if the Aeon had returned to it's resting place within me. "Well, I guess we need to catch a ride to Kilika?" Luann nudged. I smiled at her. "Yeah, but first we need to stop by home and pack a bag each, we could be gone for quite some time." Luann nodded and we both headed for home.