Ryuuteimaru initially bears a resemblance to a toy boat, but will eventually change in size and shape along with Issei's growth.
By Volume 17, Ryuuteimaru was large enough to allow Asia and Rossweisse to ride on it around the battlefield.
As of Volume 22, Ryuuteimaru has grown into an enormous flying ship adorned with the design of a dragon, capable of carrying more than several people.
Ryuuteimaru is one of the legendary Skíðblaðnir ships that were made by the tribe called Ívaldi who also created Thor's Mjölnir. Supposedly, very few of these ships were created.
In the Extra Life of Volume 13, "The Worries of the Next-Next Heir" (which takes place after Volume 12), Issei was given a familiar, the living Norse flying ship Skíðblaðnir, by Surtr Second. Although it is only the size of a toy boat, according to MacGregor Mathers, it will continue to grow and evolve into different forms by using the aura and imagination of its master as its source. Second also jokes that if Issei is going to become a "Harem King", he would need a harem palace. With Issei as its master, it is highly possible for it to actually grow into a flying harem palace.
It was briefly mentioned by Issei when he was discussing familiars with Asia. He states that he made a master and servant relationship with his familiar, Skíðblaðnir, which shows some compatibility between the two. Issei later officially names it Ryuuteimaru in Volume 14.
Ryuuteimaru later makes an appearance during the confrontation with the Stray Magicians from Khaos Brigade when Issei summons it as means of transportation as he is still unable to support himself with his Devil wings.
In Volume 17, Ryuuteimaru was summoned to support D×D against the battle with Qlippoth. Its size has changed from the size of a model toy to a ship. Ryuuteimaru was used to transport Asia, with Rossweisse guarding her, from one place to another through the battlefield to help the wounded.
Red Dragon Emperor of the Blazing Truth × White Dragon Emperor of the Morning Star: The True Dragon(s) of the Kuoh AcademyEdit
In Volume 22, Ryuuteimaru was summoned by Issei to transport him and his peerage members to the opening ceremony of the Azazel Cup. Due to the change in Issei from Diabolos Dragon.G, its size has changed once again to an enormous ship.
Ryuuteimaru reappeared in True Volume 3, who has entered an a cocoon state and was brought to the Underworld in the Grigori’s establishment to be analyzed by Shemhazai and with the assistance of Seekvaira Agares.
Powers & AbilitiesEdit
Growth: Ryuuteimaru will grow and evolve into different forms by using the aura and imagination of its master as its source. By using Issei's aura, it was able to an enormous ship or by using the Great Red aura in Issei's body, it was able to grow into a powerful armor base.
Immense Strength: Despite its small size, it can still fly while carrying it's master. Issei states that it has amazing horsepower and strength, which was demonstrated when it was able to carry him during the battle with the Stray Magicians. In Volume 22, Ryuuteimaru grew to an enormous ship with a dragon exterior which can easily carry Issei's entire team. According to Rias Gremory’s words, Ryuuteimaru in AxA, is able to destroy a planet just by one shot.
Flight: Ryuuteimaru is able to hover and levitate itself.
By using Great Red's power, Ryuuteimaru can transform into a powerful mobile armor base that Issei can pilot. The power that Ryuuteimaru has in this form is so great that it overwhelmed Tartarus, a Primordial God in Greek mythology. It has the power to destroy the entire world with it's destructive power. Because of the weapons that was installed in it, Ryuuteimaru gains new abilities in this form.
- Revelation Barrier (レベレーション バリアー, Reberēshon Bariā): Creates a stronger barrier around the body and is powerful enough to withstand attacks from gods such as Tartarus.
- Revelation Blade (レベレーション ブレード, Reberēshon Burēdo): With four arms of his Apocalypse AnswerArms form, each of the arms carries a aura blade known as Apocalypse Ascalon (アポカリュプス・アスカロン, Apokaryupusu Asukaron), which can easily cut through anything like Tartarus' tentacles.
- Revelation All-Range Blaster (レベレーション オールレンジ ブラスター, Reberēshon Ōrurenji Burasutā): Similar to Cardinal Crimson Promotion and Diabolos Dragon God, Apocalypse AnswerArms has many cannons to fire powerful blast of auras that can destroy Tartarus’ magic barriers like paper and destroys almost half of his body, even as Issei held back his power. The blast of destructive energy is so powerful it can alter the environment and is strong enough to destroy the artificial space created by Dimension Lost. Issei states that the blast is comparable to several Infinity Blaster's blast attacks combined.
- Issei named Ryuuteimaru using the Ryuutei (龍帝, Dragon Emperor) apart of namesake as the Sekiryuutei and maru (丸, circle), which was used to name ships in Japan.
- So its full name is Dragon Emperor Circle.
- According to Ichiei Ichibumi’s words, Ryuuteimaru still has unrevealed weapons which will be introduced in the future.