Here we have another "problem deity." Tiamat, of course, is the name of an established D&D deity, and the reimagining of the Therafim Deities was an attempt to break away from the classic D&D pantheon, and start something quite new and different. So why in the world am I keeping Tiamat here? At the very least, I could change her name, like the Dragonlance setting did.
I did think about that long and hard before I shrugged my shoulders and just went with the name Tiamat, like the classical Babylonian goddess of primordial chaos. I tried to go back a little bit in describing her, as http://en.wikipedia.org/wiki/Tiamat talks about the original, real-world mythology of Tiamat, identifying her as the mother of the draconic deities, just as Bahamut is the father. Still, she's got a long history in gaming, and as far as I know she's not a copyrighted creature either, and her gaming image and flavor fit fairly well into Therafim's setting without too much modification. A name is an important thing, so I didn't bother changing it, letting all that past stuff hang upon her as it always has, without trying to diminish her awesomeness.