The Reluctant Mage by Karen Miller
It's been months since Rafel ventured over Barl's Mountains into the unknown, in a desperate bid to seek help. With his father's Weather Magic exhausted and Lur ravaged by polluting magics, there seemed no other hope. Now this too has died. Only Deenie believes Rafel still lives, sensing her brother in tortured dreams. She also knows she must try to find him, as only Rafel's talents could heal their land. The prospect terrifies Deenie, yet she sees no other choice. But she finds the lands beyond Lur blighted with lawlessness and chaos - and here Deenie and her companion Charis find the dark sorcerer Morg's deadly legacy. As they travel, they learn of a dangerous new power in the land. Deenie comes to suspect that not only is her brother involved, but that the evil their father destroyed is somehow reborn. And if she can't save Rafel then, through him, Morg's vast power could once again command their world. The Reluctant Mage is the sequel to The Prodigal Mage, and set in the same world as Karen Miller's bestselling debut The Innocent Mage.