Tiamat was a unique chromatic dragon, who had one head for each primary color of the most common species of chromatics (black, blue, green, red, white). Each head was able to operate entirely independently of each other and had the powers of a member of the respective race of dragonkind. Her body also had traits in common with a wyvern, including a long tail tipped with a venomous stinger.
She also had three main avatars. The Dark Lady was a mulan woman with long dark hair and completely black eyes. She always wore dark robes and frequently had a seductive smile on her face.
The Chromatic Dragon was a dragon with stubby legs and five heads that could be any combination of head belonging to a chromatic dragon, the skin of each merged into three stripes -- blue-green, gray and purple before they merged again into brown skin that covered her tail. Sometimes, The Chromatic Dragon appeared in the form of Tchazzar when manifesting in Chessenta. The Undying Queen was a dracolich version of The Chromatic Dragon.