Someone on Tumblr speculated about Balthazar's vessel, theorizing that he was probably a holy man, a priest or something, and then along comes this debauched angel and... well, this happened.

I know canonically that Balthazar probably skipped Heaven around Season 5 or the beginning of Season 6, but since it was never explicitly stated, in my personal headcanon, Balthazar jumped ship in the 1400s.

Father Jean Roché was putting the finishing touches on the next morning's sermon when he first heard the voice.

"Jean," it said as though from far away. "Jean."

"Who's there?" he called, squinting in the low light his flickering candle gave off. Had one of his parishioners stayed behind? But no, they wouldn't have called him by his Christian name.

There was no answering whisper to his call. He waited for a full minute before shrugging to himself and dismissing it. He went back to his sermon, tucking a stray blond curl behind his ear. He normally kept his hair tied back during the day, but after all of his devoted faithful had returned to their homes, he would let down his hair. It skimmed his shoulders, and as a mark of devotion to God, he let it stay long.

By the time he retired to his room for the night, he had completely forgotten about the voice.

The second time he heard the voice, nearly a week later, one of the parish widows had stayed behind to speak with the good Father. Marie Lambaste had been widowed young at only twenty-one years old, and with three small children, the oldest of whom was barely three years old, she was struggling. Father Roché had taken it upon himself to ensure that all four of them ate daily until the widow was able to secure employment. He secretly hoped that Michel, the middle child at eighteen months old, would end up entering the priesthood. It was the only way the boy would be able to earn an education now that his father was dead.

"Jean," the mysteriously disembodied voice whispered. It seemed to come from right next to him, the barest sound of a sigh in his ear. "Jean."

"Do... do you hear that?" Father Roché asked Mme. Lambaste, looking around to see nothing again.

"Hear what, Father?"

"That voice. It's calling me."

She gave him a puzzled look. "I hear nothing, Father."

"Jean," the voice whispered again.

I must be going mad, he thought in sudden horror. He was hearing voices—either he was going mad or the Devil was speaking to him. Both prospects were terrifying, but the far less frightening thought was a descent to madness.

"Are you alright?"

"Yes, of course. It... it must have been the wind. Or my imagination." He cleared his voice. "My apologies. Little Veronica, you said she has a cough?"

It was a full month before he heard the voice again. After one week, and then another, and finally a third elapsed with no hint of the voice returning, he had assured himself that he'd imagined it. He almost laughed at himself—the Devil? Speaking to him? He was a man of the cloth. Satan should know better than to tempt him. It would be a fool's errand.

"Jean."

There it was again. The hairs on the back of Father Roche's neck stood on end. "Who are you?" he demanded, leaping to his feet from where he'd just been poised praying on bended knee. He turned in a full circle, taking in his surroundings in their entirety to see that the rest of the church was completely empty, save him. "Who are you? This is holy ground, demon!"

"I am no demon, Jean."

This was more information out of the voice than he'd gotten before. Heart hammering nearly out of his chest, he called out, "Then what are you?" He continued looking this way and that, as though the owner of the voice would emerge from the gloom.

It seemed to sigh. "I am an angel of the Lord."

There was suddenly not enough air in all of France. Father Roché gasped and reached out for the edge of the pew, the only thing keeping him standing. An angel? Speaking to me? He managed to ask, "And who am I, that an angel of the Lord should call upon me?" He didn't know why he suddenly believed and trusted this mysterious voice, but he did.

"You are chosen, Jean. The Lord has chosen you."

Every further revelation sent another wave of terror and wonder through him. "Chosen? For what?"

The voice was silent for a long moment. "I need your help, Jean. Angels are able to walk among humans, but at great sacrifice. In order for an angel to take a physical form, they must possess the body of a human. The human must give their consent for this to happen.

"I need to use you as a vessel, Jean. You must say yes to me."

What on Earth would an angel need to be here for? He could only think of one reason: the Apocalypse. "Is this... a sign of the end times?"

"No, Jean. Angels have been coming to Earth since the dawn of mankind. It is not a sign of Armageddon."

He almost breathed a sigh of relief. "There is no one else you can use?"

"It is a bloodline, Jean. You are the only human I can turn to."

Father Roché was an orphan. His mother had died in childbirth and his father passed away ten years ago. He never had any siblings, and his parents' brothers and sisters were all either very old or dead. In a way, it made sense. "Then yes," he said. "Let it be done to me as you have said."

A moment later, his eyes were filled with light, and he felt no more.

When he regained awareness, it must have only been moments that had passed. He was standing right where he had been before, but he felt a strange sort of disconnection from everything. He could see, but his eyes didn't move where he intended them. He was aware of his hand raising to his sight line, but he wasn't moving.

"Hmm," he heard his voice saying, but he hadn't been the one to speak. "That is a peculiar sensation."

What is going on? he wondered wildly. He could feel an incredible power coursing through his whole body, threatening to blow away his mind. He felt like he was barely hanging on. What is this?

Another voice, the voice of the angel, responded in his head. I have taken over your body, Jean.

This is what it feels like to be possessed by an angel?

Yes, Jean.

It's... overwhelming.

Give me a moment. As soon as the angel answered him, he felt the power diminish slightly. He no longer felt as though he could be shoved out of his own body. It rather felt like he was in the midst of a strong wind, but with no actual threat of flying away. You will have to forgive me, Jean. This is new for me as well. I have never taken a vessel before.

Oh. Jean racked his mind and suddenly, it felt as though he'd smacked into a wall that hadn't been there before. Disoriented, he asked, What was that?

My apologies. I have a consciousness, just as you do. I have memories and emotions. What you just inadvertently ran into was my consciousness.

The angel had moved into his head. He felt... afraid. Here was this celestial being inhabiting his body, and suddenly he was just along for the ride. He knew nothing about the angel, after all. He wondered for a moment if he'd made the right decision, before reminding himself that it was an angel. Angels were good, messengers of God. Of course he'd made the right decision.

I understand your fear, it said to him, and suddenly he felt the angel rifling through his memories. You are right to be afraid, but I promise you that I will not hurt you.

Jean would have nodded if he'd been able to control his own body. Do you have a name?

Yes.

What is it?

The angel hesitated. Jean suddenly wished he could go through its memories as it could clearly go through his. I doubt you will have heard of me. I am a minor angel.

I would still like to know.

Balthazar. My name is Balthazar.

The name was familiar, but not from any angelic lore. No, Jean recognized the name from Biblical canon. One of the three kings who visited Jesus after his birth, he half-asked, half-stated.

Yes. His original name was Bashazaal, but he changed it after I spoke to him. Jean couldn't be sure, but he could have sworn he heard a trace of smugness, bordering on pride, in the angel's tone. He reminded himself that angels couldn't feel pride. It was one of the seven deadly sins, and angels didn't sin.

But he felt the smile that crossed his face under Balthazar's control. The angel was using his face to smile. Jean wasn't sure why, but that thought unnerved him.

Hold on. I have heard that this is disconcerting to humans.

What is?

As if to answer his question, the world around his body shifted, melted away, transitioning instantaneously to Jean's own room with his cot in the corner. Oh. He had just enough time to register the momentary feeling of something heavy against his back, as though he'd suddenly sprouted wings for the duration of the half-a-second trip, and an impossibly short sensation of the earth being ripped away from his feet, before his consciousness failed again.

Balthazar felt the human lapse into unconsciousness again. Yes, apparently humans didn't handle flying well. This could be a problem.

Or not. Now that he had the good Father's head all to himself, he was able to fully take in and process this brand-new experience.

He didn't like this, being tethered to a human form. It felt like he was curling in on himself constantly, like he couldn't stretch out—and that was before he'd toned down his power for Jean. He didn't understand why so many angels willingly took vessels. Frankly, it sucked.

He glanced into the human's mirror and sighed. Well, at least he'd managed to land a vessel that was fairly attractive by human standards. Angel standards were a bit different, true forms considered. Still, he could appreciate Jean's physical appearance. He was a bit taller than the norm, too.

Human bodies processed physical feelings differently. They couldn't just turn off that part of themselves—they were always subconsciously aware of feeling their clothing against their skin and the ground under their feet and the wind through their hair and already, Balthazar was going mad. How was he going to live like this? Even without Jean's consciousness continually smacking into his own, the angel could tell this was going to be difficult. Humans were used to having full control of their own bodies, being able to spread out in their minds. Now, Jean was tethered inside his head, a head space he had to share with Balthazar.

Jean would probably go insane within a month. Then Balthazar would politely, calmly, mercifully offer to send him home to meet the Father, and, if he played his cards right, Jean could vacate his human form and enjoy Heaven while Balthazar went tearing around Earth in his body. He knew things would be easier once there was only one of them home, so to speak. Then he would have a little more room inside this form.

All he knew was, there was no way in Hell he was going back to Heaven.

Oh, dearie me, this was fun to write.

Never fear, there will be at least one more part to this story! I think the good Father is a little more resilient than Balthazar believes.