Ddraig

"You will know soon enough. Get stronger for that coming day. I will give you my power any time you want. However, keep it in your mind that it will come with a sacrifice of something great. I will give you something that is worth the sacrifice. You can show it to those who laughed at you. The existence of a “Dragon” that is."

- Ddraig to Issei Hyoudou in Volume 2, End Game

Ddraig is one of the Two Heavenly Dragons and the arch-rival of Albion. He is the Red Dragon known as the Welsh Dragon and Red Dragon Emperor who resides within the Longinus, Boosted Gear, wielded by Issei Hyoudou. He is feared among the Angels, Fallen Angels, Devils and the various other factions in the world for his destructive powers, which are said to be able to kill both Gods and Satans.

Appearance
Ddraig has the appearance of a large red Western Dragon with green eyes.

Personality
Ddraig's personality has changed a great deal as time has passed. At first, he had a great deal of pride in himself, though he admits that he had an intense rivalry with Albion, the other Heavenly Dragon. Since that time, he has become somewhat depressed because of the fact that he has become known as the Oppai Dragon and the Breast Dragon Emperor. Ddraig even requires counseling and medication because of it. Ddraig has shown that he cares a great deal about his current host, Issei, as much as Albion cares about Vali, despite the fact that their hosts are the ones responsible for their demeaning nicknames.

History
In the past, Ddraig fought against his arch-rival, the Vanishing Dragon, Albion, which was interrupted by the Angels, Devils, and Fallen Angels who were at war during the time. In anger, both Dragons attacked the leaders of the Three Factions, which led to their bodies being destroyed and their souls being sealed into two separate Sacred Gears, with Ddraig being placed inside the Sacred Gear "Boosted Gear".

At one point before he was sealed into the Boosted Gear, Ddraig rampaged in the Realm of the Dead along with Albion. He also fought against Grendel sometime in the past.

The Red Dragon Emperor's Awakening
Ddraig appears in the beginning of Volume 2, introducing himself to Issei. He reappears after Issei’s defeat at the hand of Riser Phenex, telling him about the "White One". Issei made a deal with Ddraig to temporally use Balance Breaker so he can face Riser again to save Rias in exchange for his left arm which was turned into that of a Dragon.

Birth of the Breast Dragon Emperor
In Volume 3, after being silent for a while, Ddraig had a conversation with Issei regarding "White One"; Albion the White Dragon Emperor, the two eventually start a teacher-student relationship, about many things regarding the mythological world and giving advice to Issei during his fights such as the later fight against Kokabiel. The said fight was then interrupted by Vali Lucifer the current host of the White Dragon who finished off Kokabiel instead, Ddraig briefly talks to Albion about the awaited match between their current hosts.

In Volume 4, After Issei meet's Vali again Ddraig explains the history between him and Albion. During the crisis with the Khaos Brigade attack, Ddraig cooperates with Issei in his fight with Vali and even supported him surviving in taking Vali's ability which created the Dividing Gear.

In Volume 5, when Issei attains the Balance Breaker after poking Rias' breast, Ddraig was happy but sad at the same time, he told Issei that he is seriously going to cry someday.

In Volume 6, Ddraig cried for the first time after hearing the television announcer of the Underworld calling Issei the "Breast Dragon Emperor" and "Oppai Dragon" after the Rating Game with Sona Sitri. Ddraig warned Rias to stay away from Issei as he was about to enter Juggernaut Drive, later while Issei was unconsciousness due to the effects of Juggernaut Drive, Ddraig explains to Azazel the usage of the form and it's drawbacks of the large amount of life span lost to the user.

The Heroic Oppai Dragon
In Volume 7 when attempting to talk to Albion, who shunned Ddraig claiming that he does not have any Breast Dragon Emperor rival, the two of them cried together. While crying, Ddraig protested, claiming that it is all Issei's fault as the two of them questioned how the two proud Heavenly Dragons had become like this.

In Volume 10, Ddraig privately contacted Azazel through Fafnir's jewel to ask him to search for a Dragon Counselor as he has been crying unconsciously.

In Volume 11, it is revealed that Ddraig suffered a broken heart at the hands of Issei, crying upon hearing the word "breast", and requires medication as well as counseling (10,000 years, to be exact). However, upon Issei's 'death' Ddraig still states Issei was the greatest host of Boosted Gear ever.

In Volume 12, Ddraig is able to capture Issei's soul and attach it to the Scale Mail, and with the aid of Ophis, transferred Issei's soul to a new body crafted by Great Red from his own flesh. After the battle with Cao Cao, Ddraig found himself exhausted, and fell into a deep sleep, after making Issei think he was dying.

The Legend of Oppai Dragon and his Lively Companions
During the first half of Volume 14, Ddraig was still sleeping after using up most of his energy to help restore Issei's body. He later awakens with the help of Fafnir and Vritra during the attack on Kuoh Academy led by Euclid Lucifuge and Grendel from Khaos Brigade.

In Volume 16, Ddraig tried to save Albion from breaking down mentally due to the appearance of Fafnir, telling him that Fafnir isn't the Dragon that they used to know and proceeded to enter a conversation with Albion, telling their possessors to be quiet for a while. Later, Ddraig was encouraged by Albion after the Two-Heavenly Dragons were mocked by Euclid Lucifuge.

Ddraig was absent for the most part in Volume 17 as he was trying to find clues on how Issei was able to use Albion's lost ability. With Albion, Vritra, and Fafnir's help, they were able to convince the past hosts of Divine Dividing to help them, resulting in Issei being able to use Dividing Wyvern Fairy freely.

In Volume 18, after searching deep within the Boosted Gear, Ddraig manages to unlock the ability Penetrate, which Issei uses to bypass Rizevim's Sacred Gear Canceler.

Powers & Abilities
Immense Strength: As one of the Heavenly Dragons, Ddraig possesses great strength. Prior to being sealed within the Boosted Gear, Ddraig's power was stated to surpass that of the current Dragon Kings. Ddraig himself claims he has the power to destroy the world a few times over simply through brute force.

Power Multiplication and Transference: Ddraig is known for his ability to multiplying his own powers or transfer that multiplied power into another being or object.

Flight: Being A Dragon, Ddraig can fly using his wings.

Penetrate: Another ability of Ddraig. It allows Ddraig to penetrate through all defenses.

Quotes

 * (To Shalba) "—You... Made the wrong choice." (Volume 6, Juggernaut Drive)
 * "I want you to remember him. The man called Issei Hyoudou." (Volume 11, Life...)
 * "Yup, my name is Ddraig. I'm a baby Dragon." (Volume 14, Life 4)
 * (To Rizevim Lucifer) "Son of Lucifer. You think you’re his enemy? Even God of the Bible revered their power — dragons. Whether it’s me, or the Hakuryuukou, or Fafnir, you can’t underestimate us — I could if I wanted, to have destroyed the world a few times over with just brute force. But I haven’t done so, because compared to you, my life is more enjoyable like this." (Volume 18, Life 4)

Trivia

 * Ddraig's name comes from the Welsh phrase Y Ddraig Goch, meaning "The Red Dragon". Y Ddraig Goch also appears on the flag of Wales as the country's national symbol.
 * If Ddraig or Albion were not sealed inside their respective Sacred Gears, their strength would place them among the Top 10 "Strongest Beings in the World".
 * Ddraig has called Issei by his name only once so far in the series.
 * Ddraig's title Red Dragon Emperor (赤龍帝) is loosely based from the name of the Pokemon Entei.