The Sky Fires. Earth Tigers, #2

An ancient enemy rises... Milyi has found her place inside the spider city, but her heart mourns for the boy she could not save. She burns for vengeance, for a chance to win back what was taken from her. When the enemy rises over the jungle, Milyi must face more than their deadly stings, she must learn to let Saku go. The Wisps seek to turn her people, to spread their poison from village to village.
The only ones who can stop them are those who defy tradition, who ride the gigantic Great Ones, and who face a trial that could easily destroy them. When Milyi's turn arrives, she must brave the most dangerous burrow of all, prove herself worthy at last, and emerge ready to fight the demons who fall from the sky like living fire.