There are different versions of everything in this story!
St. Emer, Saint Emerius, Sant Emerio or Mer, was an 8th century abbott, Benedictine monk, and legendary founder of the monastery of San Esteban de Banyoles, Spain.
Tradition places his birth at Narbonne, in southern France. Although his father was a noble, Emerius renounced the prospect of a military career to live as a hermit, journeying to the Catalonia region of Spain. Another version explains Emerius was called by Charlemagne to accompany him in his campaign against the Muslims in Girona–also called Gerona.
Several wonders and miracles are attributed to Emer. He wore some cloak, helmet or basket with a fish design, which was removed each day to feed the army of Charlemagne in its siege of Gerona. There was always enough and never failed.
But the fighting around Girona was not only against the Muslims, said chronicler Joan Amades, an eminent Catalan ethnologist and folklorist, “the Christian troops were fighting a fierce dragon and had its huge falls in the lake of Banyoles, this dragon possessed the property of flying, swimming and walking..”…his fetid breath had made life impossible for people and livestock in Selva, “and its strength was so great that the best of the French army” died by its claws or poisoned by its breath.
Emerius, arming himself with holy water, led a procession to confront the beast. In one version, he sprinkled the dragon with holy water, easily capturing and destroying it. In another version, he was sent alone to confront the monster. When Emer drew the sign of the cross on the dragon, it became tame. Emer wrapped his stole around its neck, and led the dragon “like a gentle dog” to Charlemagne.
There is another version that links the dragon to dinosaurs.
“A story from the 8th century tells of a great beast which lives beside the lake. It is the last descendant of the prehistoric beast that lived in that region. It lives in a deep cave and it is not good to disturb him.
According to what people said, the beast had a voracious appetite and it devoured the peasants’ flocks. They lived hidden at home protected by walls. In fact, every night one man disappeared from his house.
One day, Charlemagne arrived there and, having heard about the beast, he decided to go kill it. When the soldiers arrived there, the dragon came out of its cave giving off its foul breath and they began to cough because of the toxic cloud that formed around them.
After that, the peasants asked a monk to help. He had arrived with Charlemagne’s troops, and was called “Mer” (Sant Emerio).
The monk stopped them and told them it was harmless and ate only grass and roots. And when they asked him about the disappeared people he told them the truth: the disappeared people were fighting with Charlemagne who stole all the flock.
The big monster went back to its cave and even today, if somebody tries to disturb it, it will give off its foul breath against them.”