After Sumer came Baylon, the capital of Southern Mesopotamia from the early second to the early first millennium B.C. The empire's culture inherited much from the Sumerians, including their religious cosmology. However, the Babylonians and Akkadians, and the Assyrians who borrowed and adapted their myths, embellished these ancient legends, lending them a broader, more mythic scope.
One of the most familiar mythical dragons is Tiamat, the Babylonian water-demon. No mere serpent, Tiamat was a terrifying force of darkness. The gods, her offspring, were brutal and chaotic, beings who warred among themselves and created humanity as a slave race from their father's blood.
The Babylonian creation epic, the Enuma Elish, written on seven clay tablets no longer tahn the 12th century B.C., describes the dragon Apsu , god of the primordial fresh waters under the earth. Apsu was the brother-husband of the dragon Tiamat, goddess of the salt sea of the Abyss. Their waters mingled underground and created the host of gods. However, the younger gods became unruly and churned up waves disturbing their parents, who wished only rest and inertia.
Ignoring Tiamat's pleas not to fight her children, Apsu warred against Ea (also known as Enlil), which led to his destruction. enlil took over his watery realm and produced the dragon-son Marduk (also called Bel, who later became the Canaanite Baal). Marduk borrowed the powers of the other gods to make a stand against the enraged Tiamat before she could destroy them all. When the Mother of Dragons tried to swallow him, Marduk thrust a bag full of winds into her mouth, and then killed her by piercing her side with a lance. To celebrate this victory, the hero-god made the heavens and earth out of his Tiamat's body, and created humanity from her consort's blood.
Taken from "Gurps Dragons" written by Phil Masters