Theo follows!

The chamber is circular, dominated by a statue covered in glass. Kaede kneels and does the sign of the fayth.

Theo stands quietly, not moving. (He's not the summoner, so he's guessing he isn't meant to do the sign, but this isn't really standard protocol anyway.)

The ghost of a woman emerges from the statue. "Lady Summoner. You are not alone."

"I'm not," she agrees. "He is my guardian."

"Even so, guardians are not meant to be here."

"My apologies," says Theo. "We felt it important."

    "You do not wish to commune with us?" the fayth wonders.

"—well probably but first I want to ask about Zanarkand."

    "It is your final destination, summoner. You will see it when you are ready to."

"No, I mean the other one, the one where there are currently people living and stuff."

    "—ah."

"I saw it on my way back from… being inside Sin," says Theo. "And everyone there seems to be relevantly composed of magic."

"Yes," the fayth sighs. "They are. What do you wish to know?"

"Knowing what it's there for, what purpose it serves, could be helpful to figure out what I want to ask next."

"It is the dream of the fayth, as are the aeons."

"… And what does that actually do? Is it necessary for a purpose, does it sustain you somehow?"

"We sustain it. For as long as we exist in this world, and dream, our dream goes on."

"So it's not actually doing anything, it's just a byproduct?"

    "It's the goal; everything else is a byproduct."

"Goal?" asks Kaede. "Whose?"

    The fayth doesn't answer.

"… Can I ask why no response?"

"...Yu Yevon's goal."

"Yu Yevon?"

"He who crafts the soul of the dead into unholy armour. An armour called Sin."

"… And why would you be helping in that goal."

"He summons through us; for as long as there is summoning, we exist."

"So he's still around?"

"He, as Sin, is undying, in the eternal cycle that is Spira."

"… I don't suppose you know his motives?"

    She shakes her head. "If he had any, they were lost with his humanity."

"His humanity?"

    "He is but a shadow of the man he once was, from ages long past."

"… Hate to state the obvious, but – this sounds worrying."