There have been many prophecies of powerful monsters, tyrants, and cursed artifacts, and as time marches one, there are fewer left unfulfilled... and one worries the Princesses the longer it continues to not be fulfilled:

"A predator, forcefully removed from the fading light of life, will grow powerful, going on to live as guardian, saving any and all within their flooded domain, or a monster, killing for revenge."

... then, one day, they find the prophecy has begun to be fulfilled...

... mommy...?

This is a Displaced story, and if you don't like it don't read.

All ideas are primarily from MLP:FiM and Maneater