Father is a hypocrite, he thought the first time he took a life.
'Thou shalt not kill' – it was one of the commandments, yet here he was. He couldn't complain – and he wouldn't, because this was his duty and he was to fulfill it – but as the years went on, those words burned at the back of his mind like a fresh brand with every death.
He pretended to be proud of his work in the face of the other angels (not prideful, though – he could never go that far), but only because it was the task God had given him and he was to complete it happily and without protest. By the time the bubonic plague came around he lost the little enjoyment he'd had in the task and moved though people's lives with a cold efficiency, killing those who were to die and taking the souls of those who were already dead. He was grateful for the first signs of the end of days; soon enough he'd be able to write his own name in the Book and leave this hellish existence behind.
And then Sam and Dean Winchester fucked up the apocalypse.
He started hopping around the world like the Road Runner, picking up the dead left and right because the human race was outliving its destiny and that was never supposed to happen. If they couldn't all die at once like they were supposed to, they'd die in bits and pieces, and that just made everything way more difficult. It was irritating, not to get a moment's peace, called in every ten minutes for a job he never wanted and didn't enjoy.
So he fell.
At least he planned to; one can't just get up one morning and decide to change everything they know without a plan set in motion. First he had to find a vessel, though that was pretty easy – soon enough he came across a young man, barely into his twenties, with incredibly bad luck and a dangerously suicidal mind. The night he sat at the edge of his bed, a gun pressed to the underside of his chin, Azrael slipped his soul away just before he pulled the trigger and fell almost comfortably into the borrowed body.
Almost.
Forcing three pairs of wings through the vessel's back was one of the most excruciatingly painful sensations he'd ever felt; the nerves along his back ignited all at once, and goosebumps rose across his stolen skin. He grit his teeth around a choked grunt, fingers gripping at the short hair at the back of his head, and when the slightly smaller set at the small of his back finally breached the pain settled to a dull ache.
Within a few moments it began again; that tingle in the back of his mind that let him know he was needed. He tried to ignore it, of course, but as the seconds went on it grew more insistent until he had to acknowledge it. Once, he managed to disregard that irritating little itch for a good hour, but later he learned that postponing retrieval of a soul gave him the king of all migraines, so much so that he could barely function by the time he relented and went for it.
He searched for ways to dull that insight, ways to make himself available to feel when someone was dying or had died but not to the extent that he always had, or at least to still the migraines. He experimented with the humans' drugs, considering that a solution – he would be the last to die anyway; nothing could kill him until the end of days actually came to pass – and it worked, but then came the deep, burning need for more coke, more crack, more meth, more ecstasy, more heroin…
He wouldn't—couldn't touch any of it ever again.
It took an immense amount of willpower, even for an archangel, to bring the addictions down to just nicotine, but there was still an ache in the pit of his stomach that desired for more. If he ever still prayed, it would be that he'd never truly need to sink that low again.
And now, even though he'd fallen, he does as he was made to do. There is no escaping it; he's the Angel of Death and he is to act as such. There's no way around it.
And on the day of his own death, when he can write his own name in the book, no one else would be there to judge whether or not he'd followed his Father's will.