Tiamat, the Chromatic Queen, is said to be one of the first three dragons alongside Tidāhi and Theratis. She is said to be the first chromatic dragon, purely evil in her existence.
She was killed at the end of the first era during the Omniborn Crisis, when the Omniborn including Krakus used the Time Gears of Tempos to defeat her. It's said that Tiamat's death was one of the first major divine ends, and led to Tempos abandoning her favor of the Omniborn race. Tidāhi too disappeared after her death, leaving only Theratis.
It's said by some that the dragon archdevil Queen Judora is an avatar or rebirth of Tiamat.
Cults of Tiamat are rare on Abmarah by the third era, with only the oldest of dragons remembering their fallen goddess. She is also customary worshiped by Môrists as a part of their ritual practice venerating fallen deities.