Merlin's Mirror by Andre Norton

For we cannot leave this to the night!”
    Myrddin straightened, his earth-stained dagger in his hand. He tossed aside another bowl of earth. Inwardly he knew that the Druid was right—they must not leave theopened barrow during the night—though the human part of him shrank from invading a place of the dead during the hours of darkness.
    Yet he laid aside his clumsy tools and hurried back across the end of the blue stone circle, dodging among the megaliths until he reached the hut. The fire, well covered, still had its coals alive. The boy thrust two torches into the embers, then swung them around his head, letting the air feed their flames into life.
    One in each hand, he hastened back intent only on reaching the barrow. But his concentration was suddenly broken by a sensation of alarm. Though he looked from right to left and back again, he saw no movement among the stones whose shadows were beginning to reach like groping fingers over the earth. This wariness might only be because of what they were going to do. He went more slowly, however, and, as he went, he kept careful look around him.
    Once more at the digging, he drove the pointed ends of the torches into the earth. By their flickering he could see that Lugaid had not been idle during his absence, for the end of the stone block had been reached, and now the Druid was cutting his way down deeper to reveal whatever door might once have existed.
    There was another stone set there, smaller but upright, and it yielded to their combined leverage with the ax, though the tool’s metal broke into two pieces as the stone moved. Myrddin squatted down, his smaller body better fitted to the opening. Lugaid grasped the nearer of the torches and brought the fire closer to give him light.
    There were things within: jars, a brace of spears and something wrapped in a covering which puffed into dust when the air reached it. But Myrddin did not want to look at that. Instead he searched for the gleam of metal, and the fire suddenly revealed it.
    With infinite care the boy thrust his arm in the opening and groped until his fingers closed on something cold and solid. He drew it toward him, bringing a sword out into the light of the torches.
    The blade could only be of the same alloy as that scrap Lugaid treasured. Unpitted by time, straight and smooth as if it had been forged within a year, it answered the flames with a rippling of rainbow light. The hilt was wound around with wire and a great dull jewel crowned the pommel.Carefully Myrddin passed it to the Druid and then began pushing back the sealing rock with frantic haste.
    “We must hide this,” he panted. “Out there”—he did not turn his head above the trench they had tunneled—“from out there, we are watched!”
    He heard the hiss of Lugaid’s breath.
    “Then take you this, boy, and go! Leave me the light. I shall close the barrow. But this must not be risked!”
    He held out the sword and Myrddin took it once more, wishing he had his cloak to wrap that length of blade, for it seemed to gather light from the torches and reflect it again like some kind of lamp.
    Holding the weapon tight against him, he ran down the side of the barrow, heading for the hut. And the knowledge that one watched among the stones was so clear that he expected, every step of his flight, to have a challenge hurled at him.
    It could be some wandering tribesman, even a scout from a far-roving party of Saxons. And what he carried now, had they caught clear sight of it, would be booty enough to bring them down upon him. Yet he inwardly believed that the watcher was not any ordinary enemy.
    He had left the door curtain looped up when he had gone for the torches. And that fire he had stirred to life was still flickering, making a well-marked oblong to guide him.
    Myrddin was within ten paces of the doorway when a figure separated itself deliberately from one of the standing stones and ran fleetly toward him. The boy swung around to face that