Dragons opens recounting the legends of Apep, Tiamat, Jörmungandr, Nidhoggr, and Typhon. Born before time began, these creatures were sons of chaos and so the gods did battle with them for only when they were beaten could order prevail and the universe be born. Across various cultures, the same told was told with Set and Ra, Marduk, Thor, and Zeus playing the same role. The gods ultimately did prevail and these cosmic dragons were destroyed but the fight was not yet over because they left descendants with whom mortals would do battle . Cadmus’ dragon was one example.
Chinese dragons and other Asian dragons were an exception to all this; unlike their western cousins, they never lost their semi-divine status and, again unlike them, they were mostly benevolent. The creator goddess Nu Kua was herself partly dragon and Emperor sat on the Dragon Throne. The Dragon Kings governed wind and water and for the rain they sent the Chinese people loved them.
No such love was present for European dragons. While not always evil as seen with the Laidly Worm, dragons were nearly always a threat, and even when they were not, they guarded treasures that man sought, weather gold or water or something else. They had to be destroyed and Christianity, "the hammer of the dragon race," proved one of the most powerful weapons against them because it promised a world in which dragons, creatures of appetite, could have no place. Some saints killed their dragons such as Saint Margeret while others such saints Carantoc tamed theirs. Regardless of the good intentions of men like Carantoc, however, peaceful coexistence between man and dragon was almost impossible as the tale of Saint Martha and Tarasque shows. The dragonslayers rose up to destroy them as well. Saint George is the most famous example. A dragon slayer could expect to win gold, women, and everlasting glory, but it was usually a quest for survival. In the end, humans civilized the world and drove dragons to extinction.