Wings of fire. Original series volume 4
"When Starflight is stolen by his own tribe, he hopes at least to discover some of the long-held NightWing secrets -- what magical powers they really have, who they're allied with in the war, and where they've been living all this time. But the truth about Starflight's tribe is more terrible than he ever imagined: Not only do the NightWings live in a dark, miserable place, but they've imprisoned several innocent RainWings there, too. Stranded and...