Turning about, Desiderius saw that it was an Angel which spoke, and he fell at the bright spirit's feet, abashed and in great dread. But the Angel raised him up, and gave him courage, saying: "O Desiderius, most dear to me (for I am thine Angel Guardian), do not tremble to tell me; but speak to me even as thou wouldst speak to a man of thy brethren." Then said Desiderius: "Show to me and make plain, I pray thee, the mystery of the grace of God in the heart of man." "Many are the mysteries of God," said the Angel, "whereof even the highest of the Archangels may not sustain the splendour, and this is one of them. Howbeit, if thou wilt be patient and prayerful, and wilt repose thy trust in the Lord Christ, I will strive to show thee two pictures of thy very self--one, to wit, of the natural Adam in Desiderius, and one of the man redeemed by the blood shed for thee. So in some wise shalt thou come to some dim light of this mystery of grace divine. Will that suffice thee?" "That, Lord Angel, will suffice," said the monk, bowing low before the Angel. "Wait, then, and watch; and even in thy body and before thou diest thou shalt behold as I have said." Therewith the Angel left him, and Desiderius was aware of but the walls and pillars of the cloister, and the bright vast plain, and, far away, the city of Sarras glittering, and the smoke sleeping like a small blue cloud above it. And the coming and going of the Angel was after this manner. Desiderius perceived him, bright in the brightness of the sunshine, as one perceives a morsel of clear ice floating in clear water; and when Desiderius saw him no more it was as though the clear ice had melted into the clear water. Now after the lapse of three short years, and when he was but in his thirtieth summer, Desiderius was summoned from his cell on the lonely mountain, and, despite his tears and supplications and his protestations of ignorance and inexperience and extreme youth, made Archbishop of Sarras. Only one answer was vouchsafed to him. "One of thy vows was entire obedience, and the grace of God is sufficient for thee." In that same year a horde of the fierce Avars poured out from the round green earth-walls of their mysterious stronghold, which lay beyond Danube, and, crossing the river, fell on Sarras; and clashing with that ravening horde, Astulf the King of Sarras was slain.