Azrael is the "Archangel of Death". When you first encounter Azrael he is imprisoned in The Black Throne. He was the only one in heaven's forces that War had no need to fear. To free him, War must defeat the three guardians and redirect the beams to the floating heads withholding Azrael. After freeing Azrael you will be able to set out to defeat Straga. Once you defeat Straga, Azrael will open the Well of Souls to take you to Eden. Once you face the Shadow War and go to the Tree of Knowledge you will see a vision of the past truth and the truth yet to come. After you return to Azrael and The Watcher (who was forced to wait), Azrael tells you that the sword you saw in the vision is real and sends you on the journey to find the pieces of the Armageddon blade. He reveals that Abaddon manipulated him into destroying the seals in order to destroy Hell, which Abaddon saw as a threat to the universe (Save for one in order to prevent interference from the Horsemen). After War frees Azrael, War tells him that he will kill all who destroyed the balance. Azrael says he is not afraid and is ready to be punished for his crimes. After reconstructing the Armageddon Blade, War returns to Azrael, who sends him to where the Destroyer waits. It is unknown if War ended up executing Azrael, though it is unlikely considering that he needed the latter's power to get to the Destroyer's lair.
In Chaos Comics, Azrael serves Lady Death who has taken the Death Scythe, and is the personification of Death. He falls in love with Lady Death's half-sister Vandala. When the world was recreated he was altered. No longer an angel but a man with death-touch, he renamed himself Ravenheart. He continued to help Lady Death in the new world.
Azrael is a fallen angel who seeks Spawn to get the god throne for his own ends.