Dragon

Dragons (ドラゴン Doragon) are one of the most powerful and prominent creatures in High School DxD. They are beings created from masses of energy and will act freely and selfishly. Despite this, Dragons have an extremely high level of intelligence.

Dragons are creatures that represent power. As such, in all ages, Dragons are admired, respected, and feared by all. The Dragons are the only creatures whom as a race, did not side with any of the three factions in the Great War, unlike the Youkai, European monsters, spirits, fairies, and other supernatural races. However, some individual Dragons 'did' join one of the three factions.

Unlike other races that have long lifespans, all Dragons have a limitless lifespan, as they do not age after reaching maturity and will only die if killed.

Currently, almost all of the Dragons of legend are sealed in Sacred Gears, dormant, missing, or dead.

Appearance
There are two physical types of Dragons, the Western Dragon and the Eastern Dragon. The Western Dragons have two pairs of lizard-type legs, leathery wings growing from their backs, and a long, muscular tail. The Eastern Dragons have long, scaled bodies with four legs. Unlike the Western Dragon, Eastern Dragons have no wings.

Classes
The Dragons are divided into many different classes. There are the normal Dragons, the Dragon Kings which are above the normal Dragons, the Heavenly Dragons which are above the Dragon Kings, and the True Dragon and Dragon God, the highest class of Dragons.

Dragon God
The Dragon God (龍神 Ryūshin) is a class that solely belongs to Ophis, the Ouroboros Dragon and founder of the Khaos Brigade. It is one of the two classes that are above the Two Heavenly Dragons.

True Dragon
The True Dragon (真龍 Shinryū) is a class solely belonged to the Great Red, the Apocalypse Dragon and the True Red Dragon Emperor God who is known as the "Dragon of Dragons(DxD)". It is one of the two classes that are above Two Heavenly Dragons. Great Red was the only Dragon that belonged to this class. But in Volume 12, it is said that Issei could be thought of as a small True Dragon because of having his new body made from Great Red's flesh.

Two Heavenly Dragons
The Two Heavenly Dragons (二天龍 Nitenryū) are Dragons with powers that rival that of a God and Satan and are considered to be of the highest class of Dragons. The two Heavenly Dragons are the Red Dragon Emperor, Ddraig, and the White Dragon Emperor, Albion. Currently, both of the Heavenly Dragons are sealed inside two seperate Sacred Gears: Boosted Gear and Divine Dividing.

Five Dragon Kings
The Dragon Kings (五大龍王 Godai RyūŌ) are a group of five (previously six) Dragons with high destructive powers. The Five Dragon Kings are Tiamat, Yu-Long, Vritra, Midgardsormr and Fafnir. Tannin was also a member of the Dragon Kings before leaving and joining the Devils.

High-level Dragons
A Dragon class that belongs to normal dragons. There are three Dragons within this class: the Sprite Dragon, Flame Dragon, and Blizzard Dragon. Out of the three, only two, the Sprite Dragon and the Flame Dragon, have appeared in the series.

Low-level Dragons
A Dragon class that belongs to normal Dragons. The only Dragon that has been revealed and belongs to this class is the Earth Dragon.

Other Dragons
There are few Dragons that does not have proper classes due to being a former Dragon or a Dragon that has been forbidden. The two Dragons that belongs to this category are Tannin (former Dragon King) and Samael (a Dragon that has been sealed). Issei can also be considered as a Dragon of this class, as his body is made from the Great Red's flesh through Ophis' powers. This, along with the Boosted Gear, places Issei as a Dragon under the Dragon God, True Dragon and Heavenly Dragon types but at the same time he is not.

Powers and Abilities
The abilities of a Dragon differ between Classes, and specific races of Dragon, and in some cases the specific Dragon. All of them have shown the power of flight, and the ability to either breath fire, or lightning.

Dragon Gate
The Dragon Gate is a magic circle exclusive to the Dragons. The Dragon Gate allows them to summon another Dragon. While the Dragon Gate insignia can be drawn by someone else, it will only respond when there is a Dragon nearby. The Dragon Gate insignia is positioned after the Five Dragon Kings, Tannin and the Two Heavenly Dragons. Despite so, there appears to be other method to use the Dragon Gate; in Volume 9, the Hero Faction intended to use Yasaka and the spiritual energy of Kyoto to replace the use of the Dragons to open the Dragon Gate.

Trivia

 * There is a race of Dragons who require a special fruit, called the Dragon Apple, to survive. All Dragon Apples on Earth have been destroyed by climate changes, with the ones growing in the Underworld all existing within Tannin's territory.
 * The Dragon Apple was the main reason for Tannin to become a Devil.
 * Tannin is served by a number of Dragons, possibly his Peerage.