Angel Of Death's History
The Angel of Death is an ancient, powerful being that is neither good nor evil, but simply neutral. It is his job is to keep the cosmic balance leveled by claiming the souls of the dead.
Death claims the souls of those who die and takes them to the afterlife. It is useless to fight him as he cannot be destroyed for there is always death, and there is only life because of death. The Angel of Death cannot be stopped and never gives up a claim. The only way to change the fate of one destined to die is to make a plea to an Angel of Destiny.
The Angel of Death has come into contact with the Charmed Ones on numerous occasions, which is unusual as most mortal beings only encounter Death once. These meetings have formed a familiar bond between the sisters and Death, something he had never experienced before.
Meeting Prue Halliwell:
While at the beach with her sisters, Prue Halliwell suddenly saw a dark shadow following a woman. When the Seekers killed later her, the shadow appeared again and turned into the Angel of Death to claim her soul. He told Prue there was nothing she could do, as her time had come.
Prue later went back to the beach and cast a spell to summon Death. He appeared before her and taunted her about her mother, telling her she was angry about her early death. Death stated that Prue could not accept death, which prevented her from mourning her mother properly. In order to get her to accept death, the Angel took Prue to the mausoleum to witness the death of Reece Davidson.
The following day, Death told Prue that if she had not accepted death, she would have been next on his list. Prue then admitted she was angry, because she did not know what else to be. Death then told her to grieve and move on before disappearing.
Going after Miles:
Despite not appearing in the episode, the Angel of Death went after Phoebe's boyfriend, Miles, whose life has come to an end. His attempt to collect his soul is thwarted every time by Phoebe's premonitions of his dying moments. According to Bacarra, the Angel of Death eventually goes after Phoebe to stop her from messing with the Grand Design. This chain of events is eventually undone when Piper went back in time and talked herself into letting Miles die.
Clarence:
A different Angel using the name Clarence appeared to take the soul of Chris Halliwell, as he started fading away due to his parents not conceiving him yet because of his interference in the past. He posed as a janitor at P3 and talked to Chris as he was a special case. He wanted Chris to enjoy his life more. When Chris was conceived, Clarance appeared to him once more and told him not to waste his second chance.
Piper as the Angel of Death:
The Angel of Death appeared once more after Paige Matthews cast a spell on an innocent, causing him to literally become unable to die. This in turn prevented all people from moving on. After an argument with the sisters, Death temporarily killed Piper and turned her into another Angel of Death in order to repair the damage they had caused.
Death was later confronted by the Half-Demon Sirk, who convinced him to reverse the spell himself. This allowed Sirk to kill his relative. When Sirk proceeded to kill Paige, Piper appeared to take her soul, though Phoebe instead made a deal with Death to take the mortal soul of Sirk instead, so Paige could live and the balance was maintained. Death then took Sirk and restored Piper to life.
Changing Destiny:
Some time prior to the Ultimate Battle, the Angel of Death appeared before Piper once more. He informed her that Leo was about to die and offered her a chance to say goodbye, as the time he spent with the sisters caused him to become sympathetic toward them, something that had never happened before.
Piper attempted to fight Death and cast a spell to make every man look exactly like Leo to confuse and stall him. However, Death eventually found the real Leo and he was injured in a car crash. During another conversation, Death hinted there was a reason this was happening, which was why he appeared. Piper then summoned an Elder and an Avatar for answers. Both were reluctant to share information, but informed her that she needed to speak with somebody of higher power.
The sister then proceeded to summon an Angel of Destiny for answers. They then learned that Leo's death was meant to inspire them to fight the Ultimate Battle. They eventually managed to make a deal to trap Leo in ice with the Crystals used by the demon Burke, with the promise that he would be returned after the battle was fought.
The Ancient Athame:
While helping a young woman named Faith cross over after she was killed in a car crash, the Angel was confronted by a demon named Valen. Death was surprised Valen could see him and the demon abruptly stabbed him with the Ancient Athame, as it required the blood of someone caught between life and death to be activated.
It is later revealed that Death survived being stabbed by the athame, as he joined the new Tribunal to find a way to defeat the Old Ones. He presumably did not join the assault against Prue Halliwell, though it is unknown if he was among those slaughtered by her.