Tannin

Tannin is the Purple Dragon and former Dragon King, known as the Blaze Meteor Dragon. He was reincarnated into an Ultimate-Class Devil and helped train Issei in order for him to attain his Balance Breaker.

Appearance
Tannin normally appears as a purple Western Dragon that is 15 meters tall. In his mini-dragon form, he is similar in size to Asia Argento's dragon familiar, Rassei.

Personality
Tannin has a warrior-like personality and dislikes those who are lazy. Unlike other Dragons who are generally selfish, Tannin cares for his fellow Dragons, willing to become a Devil in order for his race to continue.

History
Tannin was formerly a member of the Dragon Kings, who once challenged Great Red to a fight but was ignored by him. Some time before the series, he was reincarnated into a Devil by Mephisto Pheles. He became a Devil for two reasons: the first was to participate in the Rating Games, the second was for the Dragon Apples, a fruit that now exists only in the Underworld, which a certain race of Dragons need to eat in order to survive. He then joined the Rating Games, becoming one of the Top 10 rankers and became an Ultimate-Class Devil where he gained the right to receive his own territory and chose the area where the Dragon Apples grew. He even started conducting research on how to artificially grow the Dragon Apples. Sometime before the series, Tannin entered into a semi-retired state from the Rating Games so that he could train the younger Dragons.

Birth of the Breast Dragon Emperor
Tannin made his first appearance in Volume 5, where he trains Issei in one of the mountains in the Underworld to help him attain his Balance Breaker. Afterwards, he and a group of Dragons who serve him take Rias's Peerage, Sona Sitri, and Genshirou Saji to the party for the Young Devils. Tannin later assists Issei during his fight against Kuroka and Bikou at the party for the Young Devils Gathering, which ended after Arthur Pendragon came to retrieve both of them with Tannin surprised at the fact that the Strongest Holy Sword, Caliburn, and its wielder are now under Vali Lucifer.

In Volume 6, Tannin fends off all the Devils from the Old Satan Faction who interfered in the Rating Game between Rias Gremory and Diodora Astaroth, the latter of which turns out to be working with the Khaos Brigade. He then confronts Ophis alongside Azazel. He and the Occult Research Club then witnessed the appearance of the Great Red who was floating through the Dimensional Gap. When asked by Issei whether they have fought before, Tannin said that he was ignored.

The Heroic Oppai Dragon
In Volume 7, Tannin was asked to help open the Dragon Gate to summon Midgardsormr, warning Vali that should he try anything weird, he will chew Vali. He later assisted in the battle against Loki, disposing of the mass-produced Midgardsormr's with ease. After the battle against Loki, he is seen ordering Issei in restoring the destroyed battlefield.

In Volume 10, Tannin was one of the spectators of the Rating Game between the Gremory and Bael Team.

In Volume 12, Tannin and his followers faced off against one of the Bandersnatch, disposing of the monster easily.

Power & Abilities
As a former Dragon King and Ultimate-Class Devil, Tannin is an extremely powerful Dragon that is on par with the Four Great Satans. He is also ranked among the Top 10 in the Rating Games. Tannin has the ability to transform into a mini-Dragon form that allows him to fit into small places. As with many other Dragons, Tannin has the ability to fly and breathe fire. His fire breath is said to have power rivaling that of a meteor strike.

Tannin also has the common powers of Devils.

Trivia

 * Tannin is famous among the children of the Underworld for his appearance in Rating Games.
 * Tannin's name originates from the Jewish sea demon Tannin, which is ironic in a sense since Tannin uses Dragon flames instead of water. It is also the modern Hebrew word for crocodile.
 * Tannin's peerage consists entirely of Dragons.
 * He is the first and only male Queen that was introduced in the series.
 * Tannin is one of the two reincarnated Devils introduced in the series to have reached Ultimate-Class.