Nocturnal companies known as the Herlethingus were fairly well-known in England until the time of our present King Henry II. They were troops engaged in endless wandering, in an aimless round, keeping an awe-struck silence, and in them many persons known to have died were seen alive. This household of Herlethingus was last seen in the marches of Wales and Hereford in the first year of the reign of King Henry. They travelled as we do, with wagons and sumpter horses, pack-saddles and panniers, hawks and hounds, and a concourse of men and women. Those who first saw them raised the whole country against them, with horns and shouts … but they rose into the air and vanished suddenly.
Walter Map (12th Century)