Vanyel nods, slowly. "If we - do build Sing, and it's in fact a good idea and doesn't eat the world or something, that seems fine." He takes a deep breath. "The Shin'a'in guard the remains of Urtho's Tower. Urtho was a very powerful mage who lived eighteen hundred years ago - his tower was a hub of magical scholarship, his era was more advanced in magic they we are even now. He - got into a war. Er, with Ma'ar, who was the same person as Leareth, his first incarnation. Can tell you more about that after. Anyway, Urtho had for some reason built a lot of magical superweapons, in secret. One of them got set off right at the end of the war and caused the Cataclysm."
He pauses for a moment. "...There are fifteen more. Still buried underground, in the basement of the tower which is somehow intact, the shields on it must've kept them from being set off too by all the magic flying around. I'm sure you can understand why it'd be really, really bad if more people knew that. I think even the Shin'a'in didn't know what they were guarding."