The Red Fortress - The Divided World, #2

In the impregnable red fortress, the mysterious leader of the slavers waits, accumulating power. Slavers have been taking children from across the divided world for longer than Nes can remember. While she's rescued her sibs with the help of her friends Malenie and Paza, her cousins are still missing and most everyone else has given up hope. But Nes has the shaper's sense. With it, a lock of hair will lead her to its owner and a pebble can become a truth stone.
Friends may not let friends hunt slavers alone, but if Nes doesn't succeed, she will lose not just her family but Malenie and Paza too.