Peter Nugent, writing in the Catholic Encyclopedia says, "the legendary account of his life offers little that is historically certain".

Some believe that Erhard was bishop of Ardagh before crossing to the mainland with Albert of Cashel, said to be his friend or his brother and who is also celebrated on the same date.

Said to have been appointed by Boniface, Erhard was probably a mission bishop at the court of the Agilofinger dukes in Regensburg.

Many monastic foundations go back to him, above all the famous monastery Niedermünster near Regensburg, which he himself led for a time as abbot.

[3] In the biography of Odile of Alsace, it is said that she was blind from birth, but that she miraculously regained her sight when she was baptized by Bishop Erhard.

Erhard was interred in the still-extant Erhard-crypt at Niedermünster, and miracles were wrought at his grave, that was guarded in the Middle Ages by Erhardinonnen, a religious community of women who observed there a perpetual round of prayer.

[2] Otto II, in 974, made donations of properties in the Danube valley to the convent "where the holy confessor Erhard rests".

At the close of the eleventh century, Paul von Bernried, a monk of Fulda, at the suggestion of Abbess Heilika of Niedermünster, wrote a life of Erhard and added a second book containing a number of miracles.

In the high altar in the parish church in the village of Attaching near Freising, there is a beautiful reliquary with an arm relic of Erhard.

[7] Erhard is depicted as a bishop (tabberd, mitre, staff) with a book on which lie two eyes (allusion to the healing of Saint Odilia); Odilia baptizing; with ax (either because he chopped down a sacred tree or because he belongs to the so-called mining saints).