The Swords of Draconus: The Winter Prince - The Realm of Magic, #4

LEGEND says that 'every child born of a dragon and a human is judged at birth by the Gods. If the child is born out of love, they will inherit magical powers, intelligence, physical strength, and beauty. But if the child is born out of hate, a monster of unspeakable mystic abilities and a lust for power will be born.' In the prequel to 'The Realm of Magic - Seeker' trilogy, set one thousand years earlier, Winter Prince Tarquin Draconus of the Winterlands, the youngest son of King Tancred III, is responsible for defending the northern province.
Since birth, Tarquin has been immune to magic and has a strange ability to render any mage or enchanted weapon powerless, causing people to believe he is 'cursed.' With the arrival of the Harvinder Comet, darklings crawl out of their lairs, drawn above to kill and feed on humans. Nobles and knights go missing and return to their homes changed. An ancient evil has cast its shadow on the Kingdom of Arkadia, and King Tancred III is too old and feeble to defend his realm.
His other three children uphold the Autumnlands, Stormlands, and Summerlands but refuse to believe the stories until a black dragon is spotted in the Parnak Mountains. Drawn by tales of the Drakons of Thrill-an ancient race of shapeshifting dragons-and a mighty weapon called the 'Soul Sword' that only a sha'tar can use to restore the balance between good and evil, Prince Tarquin sets out with the Winter Army to learn the truth and soon discovers some legends are REAL.