Spellstorm by Ed Greenwood

A cataclysmic surge of wild magic engulfs the realm, and a young woman who bears the rare, devastating power called spellfire finds herself at the heart of the chaos; pursued by factions that would exploit or destroy her and aided by a small band of seasoned spellcasters, she must learn to control her gift, uncover the source of the upheaval, and stop the storm of magic before it consumes the land.

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