But wonderful caves, entrances to a mysterious underworld, are common in all countries. A story is told of Friar Conrad, the Confessor of S. Elizabeth of Thuringia, a barbarous, brutal man, who was sent into Germany by Gregory IX. to burn and butcher heretics. The Pope called him his "dilectus filius." In 1231 he was engaged in controversy with a heretical teacher, who, beaten in argument, according to Conrad's account, offered to show him Christ and the Blessed Virgin, who with their own mouths would ratify the doctrine taught by the heretic. To this Conrad submitted, and was led into a cave in the mountains. After a long descent they entered a hall brilliantly illumined, in which sat a King on a golden throne and by him the Queen Mother. The heretic prostrated himself in adoration, and bade Conrad do the same. But the latter drew forth a consecrated host and adjured the vision, whereupon all vanished. The German stories of the mountain of Venus, in which the Tannhäuser remains, or of Frederick Barbarossa, in the Unterberg, or the Welsh stories of King Arthur in the heart of the mountain, seen occasionally, or the Danish fables of Holger Dansk in the vaults under the Kronnenburg, all refer to the generally spread belief in an underworld inhabited by spirits. In the year 1529 died Lazarus Aigner of Bergheim, near Salzburg, a poor man. At his death he handed over to his son a MS. account of a descent he had made into the underworld in 1484, and this was at once published and created a considerable sensation. According to his account, in the year just mentioned, he was on the Unterberg with his master, the parish priest, Elbenberger, and another, when they visited a chapel on the rock, above the entrance to which were cut the letters S.O.R.G.E.I.S.A.T.O.M., out of which they could make nothing. On returning home the priest observed that he wished that Lazarus would revisit the place, and make sure that the inscription had been accurately copied. Accordingly, next day, Aigner reascended the mountain and found the chapel again. But he had started late, having his ordinary work to do before he had leisure to go, and the evening was darkening in. As the way led by precipices, he deemed it inadvisable to retrace his steps that night, and so laid himself down to sleep. Next morning, Thursday, he woke refreshed, but to his amazement saw standing before him an aged barefooted friar, who asked him whence he came and what had brought him there. To this Lazarus Aigner answered truthfully. Then the hermit said to him, "I will explain to you what is the signification of these letters, and will show you something in vision."