The Children of the Gems

Twelve children were gifted with gems of magic. Twelve children had magic that ran through their blood, and they didn't even know it until it was almost too late. Twelve children were born to twelve different Gods and Goddesses, each having a different power than the one before them.
Twelve children were shunned from the world that they grew up in, forgotten except for one who walked amongst them from time to time. Twelve children grew up on their own, with one just turning of age.
Twelve children were needed to defeat the evil witch that captured eleven of the twelve Gods and Goddesses that they were sworn to protect.
Twelve children were born over and over again until they were ready to face the old Crow that captured them. But the question remains: Are they actually ready, or are the Gods and Goddess praying on a lost cause, and is the world that they know already dead?