The Dreaded dragon of Babylonian mythology that presided over chaos and was the scourge of the gods.
According to Babylonian Myth, Tiamat is a huge, female dragon that personifies the saltwater ocean, the water of chaos. Her other half is Apsu, which in-turn personifies the freshwater Abyss that lies beneath the Earth. She is also the primordial mother of all that exists, including the Gods.
From the union of Tiamat and Apsu (Saltwater & Freshwater) came the first Gods, Lachmu and Lachamu. These two in-turn were the parents of Ansar and Kisar and the grandparents of Anu and Ea.
It is written in the Creation Epic, Enuma elish (written approx 2000BC), that the descendants of Lachmu and Lachamu began to irritate Tiamat and Apsu so they decided to kill their offspring. Ea discovered their plans and killed Apsu while he was asleep. This caused Tiamat to fly into a rage and she wished to avenge his death. Thus she created an army of monstrous creatures, who would be led by her new consort, another one of her sons, Kingu. Tiamat was eventually defeated by Marduk, a young god born deep in the Freshwater sea.
When he murdered Tiamat he cleaved her body in half, the upper half became the sky and the lower half became the earth. The water that was within her became the Clouds and her tears became the source of the Rivers Tigris and Euphratus. Kingu was also killed and from his blood came the first humans.