Grendel

Grendel is an Evil Dragon, known as the Crime Force Dragon and one of the main antagonists of Volume 14.

Appearance
A dark green Western Dragon with silver eyes. Unlike other Dragons which are usually seen on their four legs, Grendel stands on his hind legs like a human. Issei claims that he is closer to a giant with the features of a Dragon.

Personality
Grendel is a psycho Dragon that is only interested in fighting and killing. He is a battle maniac who loves physical combat and destroying more than anything.

History
In the past, Grendel was slain by the original Beowulf but was later revived by the Khaos Brigade. He also fought against Ddraig at some point in the past.

The Legend of Oppai Dragon and his Lively Companions
Grendel appears in Volume 14 alongside Euclid Lucifuge and fought against Issei Hyoudou one-on-one until Euclid orders him to retreat.

Power and Abilities
Like most Dragons, Grendel can also breathe fire but his greatest strength lies in his defense. His Dragon scales are considered as one of the hardest and toughest scales out of all Dragons which is shown when he was able to take a punch from Issei in his Welsh Dragonic Rook form without substantial injury (aside from some blood from his mouth). He also went as far as to claim that he didn't feel a thing and that Issei was weak. He is highly resilient to physical pain, allowing him to continue to move and fight despite grievous injuries. His enhanced durability allows him to resist more damage than a regular Dragon.

He is also shown to be physically strong as his normal punch was described by Issei to be more powerful than Sairaorg Bael's punch in his Balance Breaker form, Regulus Rey Leather Rex. Aside from that, Grendel possesses great speed despite his size, a fact also noted by Issei.

Weaknesses and Vulnerabilities
Like all Dragons, he is vulnerable to Dragon-slaying items such as the Dragon Slayer swords Gram and Ascalon and the poison-like curse of Samael which is known as the ultimate Dragon Slayer.

Also, due to his high tolerance to pain and his psychotic personality, it leaves him ignorant to crippling injuries, which may disable him as he continues fighting. This has been shown when Issei dealt him a serious wound with Ascalon and he wished to continue fighting despite great injury and blood loss.

Trivia

 * Grendel is described by the author to be like Kamen Rider Ouja from Kamen Rider Ryuuki.
 * In Beowulf, Grendel is normally depicted as a troll or ogre-like figure.
 * Grendel has blue blood.
 * It has been strongly implied by Euclid Lucifuge and Sona Sitri that Grendel has been enhanced in some way.