Merlin was the son of no mortal father, but of an Incubus, one of a class of beings not absolutely wicked, but far from good, who inhabit the regions of the air. Merlin's mother was a virtuous young woman, who, on the birth of her son, intrusted him to a priest, who hurried him to the baptismal fount, and so saved him from sharing the lot of his father, though he retained many marks of his unearthly origin.
At this time Vortigern reigned in Britain. He was an usurper, who had caused the death of his sovereign, Moines, and driven the two brothers of the late king, whose names were Uther and Pendragon, into banishment. Vortigern, who lived in constant fear of the return of the rightful heirs of the kingdom, began to erect a strong tower for defense. The edifice, when brought by the workmen to a certain height, three times fell to the ground, without any apparent cause. The king consulted his astrologers on this wonderful event, and learned from them that it would be necessary to bathe the corner-stone of the foundation with the blood of a child born without a mortal father.
In search of such an infant, Vortigern sent his messengers all over the kingdom, and they by accident discovered Merlin, whose lineage seemed to point him out as the individual wanted. They took him to the king; but Merlin, young as he was, explained to the king the absurdity of attempting to rescue the fabric by such means, for he told him the true cause of the instability of the tower was its being placed over the den of two immense dragons, whose combats shook the earth above them. The king ordered his workmen to dig beneath the tower, and when they had done so they discovered two enormous serpents, the one white as milk, the other red as fire. The multitude looked on with amazement, till the serpents, slowly rising from their den, and expanding their enormous folds, began the combat, when every one fled in terror, except Merlin, who stood by clapping his hands and cheering on the conflict. The red dragon was slain, and the white one, gliding through a cleft in the rock, disappeared.
These animals typified, as Merlin afterwards explained, the invasion of Uther and Pendragon, the rightful princes, who soon after landed with a great army. Vortigern was defeated, and afterwards burned alive in the castle he had taken such pains to construct. On the death of Vortigern, Pendragon ascended the throne. Merlin became his chief adviser, and often assisted the king by his magical arts.
from Bulfinch's Mythology
