Crom Cruach

Crom Cruach is an Evil Dragon known as the Crescent Circle Dragon, and is said to be the strongest Evil Dragon. He was formerly affiliated with the Khaos Brigade's Qlippoth along with the other Evil Dragons.

Appearance
Crom Cruach has the ability to shapeshift his forms either into a human form or a Dragon form. In his human form, Crom Cruach has the appearance of a tall man wearing a black coat with a mixture of black and blonde hairs as well as heterochromic eyes where his right eye is gold and his left eye is black.

Personality
Unlike the other Evil Dragons, Crom Cruach appears to be calm and quiet as he usually leans on nearby walls when on standby. He also appears to put his objectives first, as despite his love for battle he was willing to leave after ten minutes when he was only told to hold off his enemies.

As noted by Vali, Crom Cruach is even more of a battle maniac than he is, and spent all the years he was absent training between the human world and the Underworld. When fighting, Crom Cruach prefers to fight alone, getting angry if an outside combatant interferes with his battle.

History
In the past, Crom Cruach was controlled by Balor, the Evil God from the Irish Mythology. After Balor was defeated by Lugh, Crom Cruach went around to observe the human world and the Underworld as part of his training and experience after he left the land where he resides due to finding the intrusion of Christianity as an annoyance.

Sometime in his training, he met and joined Rizevim Livan Lucifer's group in order for him to be able to fight strong foes and see the place where Dragons would reach at the end.

The Legend of Oppai Dragon and his Lively Companions
Crom Cruach first appeared in Volume 16 where he was introduced by Marius Tepes as their bodyguard. When the extraction of the Holy Grail started, he commandeered Grendel's fight and fought against Issei with his True Queen and Vali with his normal Balance Breaker and was able to successfully stall them for 10 minutes without taking any major damage.

In Volume 18, Crom Cruach took part in the invasion of Heaven. Unlike Walburga and Ladon, he only fought casually, only doing enough to fulfill his role. It was only when he fought against Issei while he was in True Queen mode that he became interested. He was winning the fight, but Walburga entered the fray. The two argued and Crom Cruach lost the will to continue the fight. He walked away, telling Walburga that she was on her own. He was then challenged to a fight by Dulio Gesualdo, which he happily accepted. He later arrived at the site of Issei's battle with Rizevim Livan Lucifer alongside Dulio Gesualdo. When Rizevim called for him to retreat with him, he silently refused, silently showing his severance of ties to the Qlippoth. Right before leaving heaven, he questioned Issei about what he was, devil or dragon, then challenged him to fight. Issei asked him to wait, so Crom left.

Crom Cruach visited the Hyoudou Residence in Volume 19 to deliver the egg of a Rainbow Dragon to repay a debt of gratitude to Tannin as he gave him food and shelter. After meeting Ophis, Crom Cruach challenged her to a fight but she replied that she cannot as she promised to Issei that she wouldn't fight and when asked if there is any way around, Ophis replied that she doesn't know.

Powers & Abilities
Immense Strength: Crom Cruach is said to be the most powerful of the Evil Dragons. After the years he spent on training himself back and forth between the Human world and Underworld, Crom Cruach has supposedly attained power on par with the Heavenly Dragons. This was proven when he was able to easily fight against both Issei and Vali, the possessors of the Two Heavenly Dragons at the same time just to stall them. He is so strong that he seemed to force Dulio Gesualdo to use his Balance Breaker, despite the fact that Dulio is forbidden to it without permission from Michael.

Immense Durability: Crom Cruach has shown that he is extremely durable, able to withstand Issei's Crimson Blaster attack that is combined with the Ascalon's Dragon Slayer ability without any severe injuries, albeit Issei only used one cannon. A considerable feat as Crom Cruach was never modified to be immune to Dragon Slayers by the Sephiroth Graal.

Master Hand-to-Hand Combatant: Crom Cruach is well versed in the art of hand-to-hand combat. He was able to overwhelm Issei during the Qlippoth's invasion of Heaven.

Shapeshifting: He has the ability to shapeshift from his dragon form to human form.

Trivia

 * So far, Crom Cruach is the only legendary Evil Dragon and one of five named Evil Dragons that left the Khaos Brigade, the other four being the mass-produced Evil Dragons that were tamed by Asia.