French legend tells of dragons which were killed, but which nonetheless caused the deaths of their killers. One was the Dragon of Lissagues in Aquitaine, which supposedly flourished about the beginning of the 15th Century. It was killed by Gaston de belzunce, but fell upon him in death, killing him.
Another dragon was the Dragon of Niort in Picardy. It was slain by Guillaume de Beauchamp who wore a glass mask to protect himself from the animal's fiery breath and accompanying fumes. He killed the dragon and then took off the mask to inspect the victim. From the corpse came a squirt of poison, which killed him.