There are no details on Azrael's early life, and he has only been known in the records of war. At some point before the Ikaruga Civil War, Azrael fought against the Novus Orbis Librarium and fought in single combat against Houichirou Hazuki - both survived, although Houichirou was able to repel the Mad Dog just by himself, becoming the only known person to have ever done so. 
During the civil war, Azrael was a thorn in the sides of all combating parties - the NOL, Sector Seven, and the Ikaruga Federation. During the Phenomena Weapon Dispossession Operation, in 2193, Sector Seven sent a mercenary squad to retrieve the Nox Nyctores - Deus Machina: Nirvana. Azrael wiped out the squad, leaving a singular survivor, their captain, who was rebuilt into Iron Tager. Azrael sustained a scar from this encounter that would come back to haunt him.
In 2197, Azrael was captured by Tager and Kokonoe, who had collaborated with Kagura Mutsuki. He was hired by an unknown Committee member in Sector Seven to retrieve the Azure Grimoire, but it was a setup by Kokonoe to lure him into an area where he could be captured. Despite eliminating many Sector Seven and NOL soldiers, he was still captured and detained in the Dog House after a fight with Tager where the latter struck at the scar he had caused years earlier. 
Placed under a Sealing Designation by Sector Seven, "Mad Dog Azrael" possesses a superhuman strength that defies common sense. Once he begins fighting, he continues in an unstoppable rampage until everything is destroyed, earning him the moniker of "Deathbringer." Released from his cell and searching for a "hunting ground," the Mad Dog sets his sights on Ikaruga.
Three years later, in the February of 2200, Azrael was released from his cryogenic cell on the presumed orders of Relius Clover and had a collar put around him by Sector Seven. He was given a mission by the committee to find the Azure Grimoire and to detain Kokonoe and Tager. The collar prevented him from being able to fight those who did not wish to fight him. He found Kokonoe in her lab and brushed off her brief assault, but was unable to capture her as she teleported away, using the assault to buy time.
Azrael would find Ragna the Bloodedge at some point, forcing him to activate his Azure Grimoire, but this battle was overwritten by the Phenomenon Intervention battle between Izanami and the Amaterasu Unit.
Later on, Azrael would find Bullet, a member of the mercenary squad he had wiped out years before. The two fought, but Bullet realized she was vastly outmatched and fled. Azrael would continue his hunt, eventually finding Tager and Litchi Faye-Ling and chased them throughout the Downtown of the 6th Hierarchical City of Yabiko. Nu-13 arrived on orders to retrieve Litchi from Relius and the pair fought against their targets until Kagura was teleported there by Kokonoe to buy time. Unfortunately for Azrael, all three of his opponents managed to escape and he was left alone with Nu until Hazama arrived and openly mocked the both of them. In the Lakeside Port of the 7th Hierarchical City of Kazamotsu, Azrael found Hakumen and Celica A. Mercury. He fought Hakumen, a dream of his, but the two of them escaped after Celica's intervention.
The Battle of Ragna the Bloodedge was set up to lure Azrael into Yabiko's Colosseum where he could be captured by Kokonoe and locked up again. He entered without warning, demolishing the other contestants before fighting Bullet. This fight was much more difficult than the last as Celica's presence made Bullet unable to use Ars Magus, while Azrael's strength was completely unaffected. He broke several of her bones, one injury was even sustained by her just punching him. Aware she would die, Ragna leaped into the arena as Bullet was carried off to the infirmary. Azrael almost managed to make Ragna activate the Azure Grimoire, but the latter's self-control and a vision of his previous fight with Azrael helped him overcome it. The two fought some more until Kagura switched in after Azrael threw a massive attack at Celica (which was blocked by Rachel Alucard casually throwing Gii in the way).
During his battle with Kagura, the Black Knight lost consciousness for just a second which stopped Azrael from continuing his incredible assault. Kagura figured out Azrael's weakness with his collar and created a delay that allowed Kokonoe to teleport him to a dimensional prison, although not before teleporting him to Tager so the latter could throw in an attack for good measure.
He bears a superhuman strength that defies common sense. Once he begins fighting, he'll attack anyone, friend or foe, and continue uncontrollably until everything is destroyed. For this reason, he gained the moniker "Deathbringer." He was sealed in a Dimensional Prison by Kokonoe, but after sensing the presence of the "Chosen," he begins acting in search of that strong prey.
Even though he was in a different dimension, Azrael managed to physically tear his way out of it. He found himself now inside the Embryo and his memories were completely unaffected, unlike most of the chosen who resided inside it.
Azrael became one of the chosen and fought against Ragna and Kokonoe, realizing they had lost their memories. He would later face against an illusion of Hakumen created by Nine the Phantom and would fight against her himself. She held back and told him to go to Ikaruga where he could fight against the chosen and Hades: Izanami herself. In Ikaruga, Azrael found Kagura, but he too had lost his memories. Azrael defeated him and later found Nu who had just defeated Bang Shishigami. They fought until Nu left when she detected a Nox Nyctores. Chasing after her, he later found Relius and they fought as well. At some point, Azrael had found Arakune and began dragging him across Ikaruga to consume the Nox Nyctores'.Azure, but rejected it. Azrael was tired of facing the same opponents and entered into a contract with Izanami - defeat the chosen and he would be granted access to fight the Gods of the world for all eternity.  By this time, most of the chosen's memories had been restored.
Fulfilling his pact, Azrael chased down Ragna and Rachel. He mocked Rachel since she had lost most of her overwhelming power and fought Ragna, but he was unable to beat him as Ragna had begun to reach the peak of his strength. Satisfied and wanting him to grow more, Azrael willingly walked away without killing either of them. Azrael skulked around Ikaruga and followed Bullet, who had still yet to regain her memories. He openly taunted her over how he killed her squadron before launching a nasty blow on her. He lamented over Amaterasu's choice of who was chosen, and left Bullet alone, completely unsatisfied.
In Kazamotsu, Azrael found Kagura and Jin after he was tipped off by Izanami and managed to rip his way into their frozen space-time. Using his strength alone, he shifted space so they were inside the Colosseum once more. He fought Kagura, who had managed to annoy him enough for him to unleash Enchant Dragunov to level 4, making him faster than the eye could see, but he was trapped by the combined efforts of Trinity Glassfille and Jin, who unleashed the Mucro Algesco: Yukianesa and froze him solid. 
Azrael's data was backed up by Es, and he was restored in the new world created by Ragna after Doomsday. He was kept in the dog house once more, with Kokonoe keeping a constant watch over it at all times. 
- BlazBlue: Variable Heart, Chapter 12
- BlazBlue: Chrono Phantasma Extend, Story Mode, Kokonoe "Collisions", Chapters 7 - 9
- BlazBlue: Chrono Phantasma Official Site (JP), Azrael
- BlazBlue: Central Fiction Consumer Edition Official Site (JP), Story - Azrael
- BlazBlue: Central Fiction, Arcade Mode, Azrael, Act I
- BlazBlue: Central Fiction, Arcade Mode, Azrael, Act II
- BlazBlue: Central Fiction, Arcade Mode, Azrael, Act III
- BlazBlue: Central Fiction, Story Mode, Episode 11, Chapter 090
- BlazBlue: Central Fiction, Epilogue