|Romaji||'Ao' no Hekatonkeiru|
|Light Novel Debut||Volume 1|
|Manga Debut||Chapter 0|
|Anime Debut||Episode 1|
Hekatonkheir ('青'のヘカトンケイル, 'Ao' no Hekatonkeiru) is one of the Dragons that appear in the Unlimited Fafnir series. Although it was considered to be the blue Dragon, it was eventually revealed that it was a fake Dragon created by 'Black' Vritra as a stand-in avatar for the purpose of spreading genes that would give birth to more Ds, as well as fighting against 'Green' Yggdrasil.
Hekatonkheir is portrayed as a blue phosphorescent giant covered in scales with elongated limbs and random geometric patterns shining on his skin. Instead of a head, Hekatonkheir only has a large horn growing from its neck. In the anime, Hekatonkheir lacks its scaly appearance and has a head with what seems to be multiple deformed eyes on it. Its body is entirely made out of dark matter.
After Vritra went into hiding in order to escape from Yggdrasil, she created Hekatonkheir at an unidentified time to act as her proxy, using her daughter, Kili Surtr Muspelheim, as a relay to control it. Hekatonkheir resumed Vritra's plan by spreading genes that would awaken more Ds with success until it arrived at Nanato City. There, it was destroyed for the first time by Yuu Mononobe's Anti-Dragon Armament, Marduk, which he obtained by forming a contract with Yggdrasil. Some time later, it was recreated by Vritra.
Hekatonkheir reappeared in Midgard Academy in Volume 2 to aid Kili in retrieving Tear Lightning. Although it proved to be a difficult opponent, it was once again destroyed by Yuu, who used Marduk's special artillery, Megiddo, against it.
A third and final Hekatonkheir was created by Vritra to take out Yggdrasil's main body in Volume 5. Although Hekatonkheir successfully self-destructed, taking down Yggdrasil's body with it, this action proved to be futile, as Yggdrasil's core merely moved into another body. Furthermore, this enabled the green Dragon to track down and capture Vritra.
Powers and AbilitiesEdit
Regeneration: Hekatonkheir is very resilient, able to regenerate from most injuries with ease, and can even revive after being completely destroyed (although it's likely that Vritra merely makes a new Hekatonkheir after the previous one is destroyed).
Shapeshifting: In Volume 2, Hekatonkheir displayed the ability to extend its limbs in order to reach faraway targets.
Self-destruction: In Volume 5, Hekatonkheir showed that it was capable of self-destruction, with the ensuing explosion being powerful enough to completely destroy Yggdrasil's main body and ravage the surrounding area. This is possibly done by transmuting its body made of dark matter into explosions.
- Hekatonkheir's name is derived from the Hekatonkheires, three powerful giants featured in Greek Mythology who helped the Gods overthrow the Titans.