The Sky That Broke the Hills by T.C. and R.E. Rubright

Young Feldregor “Slaga” Boyden is a mim, a military indentured man, in a backwater army post in Stheara. As he and his friend Floort try to pawn a mysterious watch, he learns painfully that he was born with a condition called sharna macha, in which contact with magic makes him violently ill, but can’t kill him. Just as Floort is about to be unjustly hanged, the fort is attacked by a fierce band of uplanders and something more sinister: a wizard storm controlled by a powerful, unseen mage. Slaga escapes with Floort and a former enemy, Major Dietrick. They go in search of Bill Skye, the Master Witch Warden. He alone can train Slaga to tame the sharna macha and turn it to his advantage. On the road they encounter bandits, dodge cavalry and bounty hunters, meet a wayward airship and more, while Slaga learns what he can do to magic and what magic can do to him.

Category: Fantasy – Coming of Age