A French legend tells the story of a fire-breathing dragon named La Gargouille that terrorized the inhabitants of the town of Rouen. It swallowed ships and spouted so much water that it caused flooding. The townspeople tried to appease the dragon each year without success by offering the sacrifice of a virgin.
A priest named Romanus agreed to vanquish the beast in exchange for the townspeople’s conversion to Christianity. He tamed the dragon by making the sign of the cross, and all but the dragon’s head was burned at the stake. As the head wouldn’t burn (immune to the flames) the townspeople cut it off and affixed it to their church where it became a warning to other dragons.
It became the model for future stone gargoyles as a protection against evil.