Ariadnis by Martin Josh
Back then I thought that if it weren't for that cliff our cities would be one and there would be no need for all this fierceness toward each other. But then I learned about pride and tradition and prophecy and those things are harder than rock. Joomia and Aula are Chosen. They will never be normal. They can never be free. On the last island on Erthe Chosen Ones are destined to enter Ariadnis on the day they turn eighteen. There they must undertake a mysterious and deadly challenge. For Joomia and Aula this means competing against each other to end the war that has seethed between their cities for nine generations. As the day draws nearer all thoughts are on the trial ahead. There's no space for friendship. No time for love. However much the girls might crave them. But how you prepare for a task you know nothing certain about? Nothing except that you must win at whatever cost or lose everything.