The Cursed Kingdom - The Sevenwars Trilogy, #3

Heart-broken over her sister's decision to walk a destructive path, Cahri is trapped in a curse that has kept her from amending what Seven Wars has done. Freeing herself from the tangled threads of her past is one thing---helping the others to defeat her sister is another, and the master sorcerer must choose between the power she has gained and the calling that is her birthright by blood. Lostland has hidden Eithe for years; he views his curse as a befitting punishment for bringing Seven Wars into existence.
But when the chance comes to face disaster and the consequences of his choices, to hopefully rectify them, Eithe finds he won't have to face Seven Wars alone. Time is running out for Team Spooky. Seven Wars holds all three anti-curses, the god of Chaos seeks to unravel everything, and magic itself is bending backwards under her command...