The sirens. Adagio Dazzle, Sonata Dusk and Aria Blaze. As we all know, were defeated in Rainbow Rocks.
But what if that wasn't it?
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Princess Twilight Sparkle, Princess of friendship. Asks princess celestia about who really are the sirens. And how they came to be equestria's second greatest threat.
Some things might just be better not to know.

(THIS STORY HAS ULTIMATELY FAILED ME. IM NOT GONNA DO ANY MORE CAUSE I REALISED I AM A BETTER READER THEN A STORYTELLER. But seriously though, what on earth happened? I don't remember typing the description up there.)