Devils of Calamity

Devils of Calamity also known as the Lucifer's Sins is a name to describe six abnormal devils, who were at one point ordinary spirits who became devils after being transformed by the influence of the Underworld. They play roles of various significance in Dragons of the Apocalypse. They all possess the power of either Ultimate-Class Devils or Upper High-class devils with Nemesis and Alastor being the strongest of the group. After the death of Alastor and later the death of Crowley, the group has since disbanded with the Seven Great Satans believing them to be gone for good. It is revealed that the 72 Pillars blame the Old Satan Faction for Alastor's mayhem and Crowley's crimes, as the former Great Satans refused to stop them and in some cases even covered up their crimes.

Summary
The Devils of Calamity were devils created without the use of Soul over Soul, making them very powerful devils and siblings in a way, with Alastor birth predating the Birth of Christ. During the Great War, the other four Devils of Calamity refused to fight in the Great War while Alastor and Crowley both took pleasure in torturing and killing other beings. Even Nemesis, who was on par to Alastor would shudder when near him due to the intense psychotic nature he possessed. Even stating she wanted to kill all of Alastor's children out of fear of who they would become. When the Devil Civil War came to a end, after the death of the former Old Satan Faction Heads and with both Alastor and Crowley dead, the remaining four feared that Nicholas Satan and the New Satan Faction would eventually turn on them and as a result they split up and hid in the human world.

Alastor
The oldest and most powerful of all the devils. Alastor is revealed to be a sadistic and sociopathic individual, who enjoys torturing and hurting other creatures, even other devils. In flashbacks, Caesar Lucifer has stated that Alastor, due to his origin, felt detached from anyone and everyone believing himself to not truly be a devil or a spirit, simply a monster. He was originally a weak spirit who was exorcised and sent to Hell by a unnamed drunken wandering priest. He however befriended the Four Great Satans and tortured hundreds to thousands on their orders, and used the Crowley's Pit as his main hunting ground. During a brief pause in the war, he later experimented with his soul creating a special form of power that he became the progenitor of known as the Power of Soul, which allowed him to manipulate his own soul and the souls of others as the basis for demonic magic. He was later slayed by the Bael Clan and their allies after he had committed numerous atrocities to other devil families.

Special Power: Power of Soul

Nemesis
The Spirit of a highly religious young girl, who had taken a oath of chastity. She was however murdered by a individual who disrespected the Gods she worshiped and as a result of her gruesome death she became a spirit who wandered killing any who disrespected the Gods. Because of her actions and mistranslated literature as times passed, some thought of her as a minor Deity who enacted divine retribution for those who practiced arrogance among the Gods rather than a simple spirit, who merely took vengeance in search of the one who killed her. After centuries of wandering, she later met a devil who was on the verge of dying, having been left for dead by a group of exorcists. After a conversation that Nemesis described as lasting a eternity between the two where they talked about life, death, greed, the law of God, the law of the Gods, and even the Underworld, the devil realizing he had little life left, willed his being with Nemesis, and as a result he was spared from death, living inside of Nemesis, and transformed her from a simple spirit to a devil. She later met Alastor in the Underworld who described her as having the same aura as him, she was then brought before the Four Great Satans and revealed to be the second abnormal devil. She turned down their request to become a soldier in the war and lived as a actress until she fled the Underworld.

Trivia

 * They all have names of Greek origins and were originally meant to be based off of the horses of Hades' chariot however this idea was discarded.
 * Two out of the Six Died before the start of the canon series.
 * It is revealed that all six of them had minor faith followings of various degrees, making them almost like pagan Gods in nature.
 * The Secondary Name was based off of Sona's Sins, a group name coined by Houki Minami.
 * While Alastor plays a center role in Heavenly Dragon Kings' Rebirth, the other Devils are never mentioned or even referenced to and play no role in the story, with the exception of Crowley.