Tiamat is the goddess of Chromatic Dragons. She goes by the name Takhisis in the Dragonlance reality.
Tiamat was first introduced to D&D with Greyhawk (1975). Details on her were provided in Monster Manual (1977) and Dragon #38 (1980). In the first edition of Deities & Demigods (1980) she is mentioned under the Babylon god Marduk ("His battles with Tiamat are legendary.") effectively stating that the Babylon Tiamat and the D&D Tiamat were one and the same. This also boosted her power level from a 16 hit dice monster with 128 hit points to a full blown goddess adding Command (no saving throw), Comprehend languages, Detect alignment, Gate, enhanced versions of Geas and Quest (no saving throw), teleport, and True seeing to her abilities.
While her rulership the first plane of The Nine Hells had been established in the Monster Manual her formal role was expanded in "The Nine Hells Part I," Dragon #75 (1983) and Manual of the Planes (1987).
In AD&D2 Tiamat got a formal goddess treatment in Monster Mythology (1992)
Tiamat got a D&D 3.x revamp which was first shown in Dragon #272.
Tiamat was written up in her Babylon form in GURPS Fantasy which gave the details of the Enuma Elish: She was the ruler of salt water and via her husband Apsu gave birth to the younger gods. The battles and celebrations these children made so much noise that their parents were angry with Apsu vowing to kill them. Tiamat protested but changed her mind when a preemptive attack by their children resulted in the death of Apsu. In exchange for becoming their leader her son, Marduk, promised to kill her which he did. Marduk then cut Tiamat’s body in half, making half into the sky and the other half into the Earth. But every year Tiamat starts to revive, flooding the land, and Marduk must kill her again.
- ↑ 4th Edition Draconomicon