What's the name of this book?
 

The main character is a preteen or teenage boy, and he lives in an island with an evil man who makes all the boys that live on the island fight with each other for his amusement. For some reason I remember salt. He has one best friend on that island and one main enemy. He's always referring to himself as made of stone (figuratively, as is he's strong). For some reason "eagle" comes to mind.