A fairy tale by Ludwig Bechstein: Thassilo in LorschLudwig Bechstein: Deutsches Sagenbuch 56. Thassilo in Lorsch
Now it happened that Charlemagne came into conflict with Thassilo, the Bavarian Duke, who was his close relative. Through incitement this Thassilo became adversarial causing Charlemagne to take terrible revenge and issue severe punishment. He had the Agilolfinger Duke blinded by forcing him to gaze into a shield made red hot by fire, until the light of his eyes went dark and then vanished entirely. His long hair was then cut before the throne and per the Kaiser’s edict, he was taken to live in a monastery as monk.
There after many years, it happened that Charlemagne rode out toward Lauresheim, which is the monastery Lorsch. He had long forgotten Duke Thassilo and was compelled to spend the night in the cathedral and pray. So he was astounded that a monk, who was blind, came walking guided by a radiant messenger of God. The Kaiser recognized the old man’s movements but could not remember his name. The monk was led from altar to altar, prayed and then retreated with his celestial guide.
The next morning Charlemagne called the abbot of the monastery and asked him the name of the monk who was served by an angel. The abbot was amazed and did not know how to answer. Following the Kaiser’s command he waited with him the next evening to watch.
And so it happened like the prior night: a blind monk came again led by an angel. The Kaiser and the abbot followed the monk and his guide back to his cell, but there only found the monk. The abbot knew the monk by his monastery name but otherwise nothing about him. The abbot addressed him and told him to state what he had been in his former worldly life; he should not not conceal or hide anything because it was his master and Kaiser who stood before him.