Tiamat

Tiamat is a female Dragon and the only female among the Five Great Dragon Kings. She is a Blue Dragon known as the Chaos Karma Dragon, and is one of the few active Dragons in the series.

Appearance
A blue Western Dragon.

Personality
Not much is known about her personality, besides the fact that she hates Ddraig for unknown reasons.

History
One of the Five Great Dragon Kings, Tiamat is one of the few legendary Dragons that are still active. She is known to be rampaging around the world occasionally.

The Red Dragon Emperor's Awakening
While Tiamat has yet to appear in the series, she was mentioned in the side story "The Familiar's Requirements" by the Familiar Master as a candidate for a powerful Familiar.

Birth of the Breast Dragon Emperor
Ddraig also mentioned her in Volume 4, when he was explaining about the Five Dragon Kings to Issei, telling Issei that she hates him.

The Legend of Oppai Dragon and his Lively Companions
She was mentioned once again when Issei and Azazel were talking about the Evil Dragons. During the conversation, Tiamat was said to be the strongest among the Five Great Dragon Kings and has blended in well with the current world and living as she likes.

Powers & Abilities
Immense Strength: The strongest Dragon King out of all the Dragon Kings. According to the Familiar Master, she has Satan-level powers.

Trivia

 * Tiamat's name is derived from the Babylonian sea goddess Tiamat. Also, Tiamat's title, the Chaos Karma Dragon, is derived from the fact that the mythological Tiamat is a chaos monster.
 * Tiamat is the only Dragon King who has yet to appear in the series.