Prophecy: Clash of Kings (Prophecy Trilogy 1) - M. K. Hume

The first in an epic trilogy charting the legend of Merlin.The legend begins...In the town of Segontium, a fugitive is washed ashore. He brutally rapes the granddaughter of the king of the Deceangli tribe, leaving her to bear his son, Myrddion Merlinus. Spurned as a demon seed, the boy is raised by his grandmother and he is apprenticed to a skilled healer who hones his remarkable gift. Meanwhile, the High King of the Celts, Vortigern, is rebuilding the ancient fortress at Dinas Emrys. According to a prophecy, he must use the blood of a demon seed to make the towers stand firm. Myrddion's life is in jeopardy. But the boy has a prophecy of his own and a richer destiny to fulfil. Soon Vortigern shall be known as the harbinger of chaos, and Myrddion must use his gifts for good in a kingdom besieged by evil. So begins the healer's journey to greatness...