Lightlark (The Lightlark Saga Book 1) (Volume 1) by Alex Aster (Author)

Welcome to the Centennial.
Every 100 years, the island of Lightlark appears to host the Centennial, a deadly game that only the rulers of six realms are invited to play. The invitation is a summons—a call to embrace victory and ruin, baubles and blood.
The Centennial offers the six rulers one final chance to break the curses that have plagued their realms for centuries. Each ruler has something to hide. Each realm’s curse is uniquely wicked. To destroy the curses, one ruler must die.