June 17 - Son of Hyvarnion, a bard from Great Britain and Rivanone who is said to have lived for a time at the court of the Frankish king Childebert, Hervé, born around 520, is blind from birth. His parents would have lived in the manor of Lanrioul in Plouzévédé. After the death of her husband, Rivanone would have settled on the territory of Keran, where she would have raised her son still in his infancy.

Hervé, after having been a disciple of the monk Martianus (or Harchian), would have lived near Saint Urfol, probable uncle of Saint Hervé. His nephew, the future Saint Hervé, had by revelation knowledge of the death of Saint Urfol and set out for his uncle's oratory. He prostrated himself there to pray and during his prayer the ground shook so hard that all those who were with him were thrown to the ground; the ground opened and from this opening came a sweet and fragrant odor. Saint Hervé, having known and found his uncle's tomb by this miracle, accommodated it with stones, and the place soon became the scene of miracles. This is surely the origin of the cult which is still rendered to Saint Urfold in Bourg-Blanc.

After the death of his mother, who, after a life "in solitude", would have died on the present site of the parish church of Lanhouarneau, Hervé stayed for a time in the oratory she had built there and he opened a school. He fled the world to lead the life of a hermit, but he was soon joined by disciples; he left Lanhourneau to return to Bourg-Blanc where, at first, he did not find the monastery, now in ruins, where Saint Urfold had lived. A miraculous earthquake brought to light the place where his uncle was buried. Hervé accommodated him with stones. He then went to Saint-Pol-de-Léon where the bishop, Saint Houardon, conferred minor orders on him, he became confessor while humbly refusing the title of abbot, accepting only to be ordained exorcist, refusing to become a priest, considering himself unworthy to celebrate the Eucharist.

Back in the Land of Leo, he delivered a count, called Helenus, from a devil who had taken his place in his domesticity. Then Saint Hervé returned to live in Lanhouarneau where he died, surrounded by his disciples, his niece Saint Christine, and so on. Some of his relics are kept at Lanhourneau. Most of his relics were given by Duke Geoffroy to the Bishop of Nantes in 1002, but they disappeared from the cathedral during the French Revolution.