The Veiling of the Moon Kingdom The Stars - Caitlin Zura

In a world where magic has long since disappeared, ten-year-old Elodae Kenton washes ashore on the beaches of Samarok, remembering only her name. She's taken in by the king and raised alongside the princess as his niece.
Thirteen years later, Elodae battles to remember her past, as a threatening darkness terrorizes the city. Across the sea, the distant moon-shaped island, Lunala, claims to have the answers that will save their people. But Lunala has spent millennia veiling their Moon Kingdom from outsiders. No one has been allowed in—or out. Until now.
A battle of the mind becomes a battle of the heart as Elodae learns to let a castle guard through the walls of her soul.
When her worst fears come true at the hands of a cruel lord—she must decide whether to let the darkness consume her.