The Lost Sentinel by Suzanne Rogerson

The magical island of Kalaya is dying, along with its Sentinel.
The Assembly controls Kalaya. Originally set up to govern, they now persecute those with magic and exile them to the Turrak Mountains. Tei, a tailor’s daughter, has always hidden her magic but when her father’s old friend visits and warns them to flee to the mountains she must leave her old life behind.

On the journey, an attack leaves her father mortally wounded. He entrusts her into the care of the exiles and on his deathbed makes a shocking confession.

Tei joins the exiles search for their new Sentinel – the only person capable of restoring the fading magic. But mysterious Masked Riders are hunting the Sentinel too, and time, as well as hope, is running out.

Against mounting odds it will take friendship, heartache and sacrifice to succeed, but is Tei willing to risk everything to save the island magic?