Roots and Steel by Casey White
Where monsters go, hunters follow. Hunters of the guild wait all year for the Festival of Knives, when they put their skills to the test and claim new ranks with every fiend they slay. Trapped helping the family business instead of pursuing his own career, Trellin has never been allowed to participate. But when he risks expulsion to sneak out and claim a kill beyond his rank, his hunt is spotted by a senior guildmember. Rather than turn him in, she offers him a chance for freedom: Join her, and sail to the distant isle of Deldynne to compete in the bloody race for the rank of Guildmaster. If they can kill the monster that calls Deldynne home before the other teams do, he'll soar to new heights as apprentice to the leader of the Hunter’s Guild. But not everyone wants his new mentor to be Guildmaster - and if they fail, neither will leave that island alive.