Kalen's Sword: The Awakening Book 1

When Kalen, the God Protector of Atlantis, departed the mortal world, he promised that a child would be born to Atlantis in a time of great need and sorrow. Kalen foretold that this boy would one day wield his mighty sword.
Standing on the mainland, Tarn, Kalen's child of prophecy, watched Atlantis slip beneath the waves in a pyroclastic cloud of fire and ash. Kalen did not foretell that Tarn would be but a child when Atlantis sank. He never mentioned that Tarn would be battle-trained in Asgard. He did not portend that Tarn was destined to be the last warrior of Atlantis.
Ill-suited to his fated role, with only his warrior training to protect him, Tarn must face Wotan, the God of the Hunt, and all who worship him. Beset by dark wizards and their followers, Tarn must find Kalen's sword and then learn how to harness its powers. First, however, Tarn must unravel Kalen's prophecy and become a Guardian Defender, the last warrior from Atlantis.