The [bad word] King Vortigern decreed that a mighty tower should be built for his pleasure. But the tower collapsed before it was finished, and his magicians told him that he must sacrifice a child and lay the body beneath the cornerstone or it would never [bad word]  But it could not be any child — it must be the child Merlin, whose father was said to be a demon and whose mother was said to be a mighty sorceress. Accordingly Merlin was seized and brought before Vortigern, but before he could be sacrificed, he spoke with the voice of prophecy and held them all in silence. 'Beneath the cornerstone of the tower lies a spring; guarding the spring are two dragons, a white and a red, and it is their ceaseless striving that has caused the tower to fall. Dig beneath the cornerstone and you will release them to finish their battle in the sky above.' So they did dig at Vortigern's direction, and the dragons sprang forth even as Merlin had said.