Shadowmarch by Tad Williams

In a world teetering on the brink of chaos, the ancient boundary known as the Shadowline, which separates the human lands from the mysterious and magical Qar, begins to shift, threatening the fragile peace. As the enigmatic forces of the Qar advance, the royal family of Southmarch finds itself embroiled in political intrigue and dark secrets. Young twins Barrick and Briony Eddon must navigate a treacherous landscape of betrayal, ancient prophecies, and hidden truths to protect their kingdom and uncover the mysteries of their own lineage. Amidst the encroaching shadows, alliances are tested, and the fate of their world hangs in the balance.

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