Tides of Fate. The Chronicles of Talahm, #3

Nothing is more important than saving Bethany from The Night's Empress. In the aftermath of losing Bethany to Langoth, Emma's magic fails with every effort to rescue her. Desperate to save her best friend, Emma and her brother Luke will stop at nothing to bring Bethany home. With an eclectic band of allies, they set sail across the portal-riddled ocean to Perga's Scepter, an island in the far north with the last stable obelisk.
From the highest mountain's peak to the depths of The Shadow Star library, it's a race to save Bethany and sentence Igraine to the black hole on the verge of consuming Langoth. But time isn't the only thing against them. When Luke starts having Vision-like nightmares right as the journey gets underway, he doesn't know who to trust besides his family. As the threads between the Pendragons and the Artairs start to unravel, Bethany's ultimate fate hangs in the balance.
In the struggle between heart and kingdom, one is sure to lose.