The Prince of Shadow (Seven Brothers, Book 1)

the long version

Llesho was only seven when the Harn invaded his family's mountain kingdom of Thebin. His guards slaughtered before his eyes, he was carried off and sold into slavery on Pearl Island, as far as he knew the sold survivor of his royal family. At fifteen, Llesho's life was forever changed. It was revealed to him that all six of his older brothers were still alive and had been sold into slavery in distant lands. Llesho must win his freedom, find and rescue his brothers and with their help raise an army against the evil Harn and reclaim his homeland. The only way a pearl diver ever found freedom was in death, and so Llesho did the unthinkable. He petitioned his lord to be trained as a gladiator, thus taking the first step that would lead to conflict with sorcerers, encounters with the avatars of gods and a dangerous journey in search of his widely scattered family... -- from the cover