The Celts had beliefs resembling those of the Greeks and Romans about incubi. Demons called dusii sought the couches of women out of lust, a belief reported by sub-Classical authors. The Classical evidence for Celtic belief in divine descent is also furnished by the form of several proper names which have been recorded, while lineage from a river or river-god is associated with the Belgic Viridomar.25
A legend reported by Pliny concerns some natural product, perhaps a fossil echinus, in explanation of the origin of which this myth was current, or to it an existing serpent-myth had been attached. Numerous serpents collected on a day in summer and, intertwining, formed a ball with the foam from their bodies, after which their united hissings threw it into the air. According to the Druids, he who would obtain it must catch it on a mantle before it touched the ground and must escape hastily, putting running water between himself and the pursuing serpents. The ball was used magically.26
Classical observers cite vaguely some myths about the otherworld and they admired profoundly the Celtic belief in immortality, which, if Lucan's words are correct, was that of the soul animating a new body there. Diodorus also affirms this, though he compares it with the Pythagorean doctrine of transmigration;27 yet in the same passage he shows that the dead passed to another world and were not reborn on earth. Irish mythology tells us nothing about the world of the dead, though it has much to say of a gods' land or Elysium, to which the living were sometimes invited by immortals. This Elysium was in distant islands, in the hollow hills, or under the waters. Plutarch, on the authority of Demetrius, who may have been a Roman functionary in Britain, reports that round Britain are many desert islands, named after gods and heroes. Demetrius himself visited one island lying nearest these, inhabited by a people whom the Britons regarded as sacred, and while he was there, a storm arose with fiery bolts falling. This the people explained as the passing away of one of the mighty, for when a
