Author's Note:

Hello everyone and welcome to my Three Houses AU. This one uses a similar principle to one of my 'How to Train Your Dragon' stories, and the intention is to eventually cross the two over. In short, its an AU where summonings from the Final Fantasy series exist in Three Houses' world, but with a load of different rules from their home games. It focuses on Dedue and Raphael, my two favourite characters, and it will deviate from the original material a fair bit. I hope you all enjoy the chapter.

I do not own any aspect of Fire Emblem: Three Houses or the Final Fantasy summonings.

Prologue

18th of the Harpstring Moon, Imperial Year 1162

A young couple fondly watched their sleeping baby, observed by an older man who sat in silence. Raphael, currently fast asleep, had arrived in the early hours and much later than expected. By now, it was long into the night, the day consumed by looking after Raphael and his mother after the birth. At this stage, the boy could be summed up in a single word.

Big.

He had a big body, could make a big noise, and had a big appetite to go with all of that. All the healers that had looked at him had agreed that he was going to stay that way, and the family had jokingly wondered where he got his size from since most of them were pretty average in that regard. They then decided that his great-grandfather's size had skipped a couple of generations, he'd been a top War Master in his time, but two people knew that the boy's size wasn't the only thing that had skipped generations.

As the couple continued to watch over their sleeping child, the older man looked to his wife, who'd been quietly tidying around the room, and they came to a silent understanding. The man spoke, "Well, we should leave you two to get some rest, you know he won't sleep long enough to give you a decent night's sleep."

The young man turned from his son, "Are you sure father?"

He smiled, "Don't worry son, we're not going far."

His wife agreed, "Indeed, and don't hesitate to come to us if you need any help."

Bidding their farewells, and promising to return in the morning, the new grandparents took their leave, soon exiting into the cool night air. The house they left was bigger than those of most commoners, the boon of having a successful business, and had been inherited from the two people who now slowly walked to their own, more modest, home nearby.

They made sure to be well out of earshot before broaching the topic that was on both their minds.

"Are you certain that he has the ability."

His question was deliberately cryptic, couldn't be too careful after all, but his wife understood.

"Yes, the mark is on his right shoulder. Thankfully, everyone there was far more concerned with the birth, I managed to magically hide it before it was noticed."

He gave a sigh of relief, "That's good."

There was silence for a bit, until she sighed herself, "I'd hoped it'd not manifest in anyone, especially since it didn't with our son."

"But we never could be sure it wouldn't." He pointed out, "The ability to summon is passed down through bloodlines."

"I know, but I've never heard of it skipping a generation before." She looked at him, her face creased with worry, "Maybe we should've told…"

"We had good reasons not to."

She nodded resignedly, "I know."

Summoning, an ability that was rarer than crests, and didn't have nearly the prestige. It was dogmatically treated as a sin and an affront to the Goddess, the church claiming that summoners meddled in the order of nature and her will. This meant continent-wide persecution and hostility, with any discovered summoners finding swift and harsh judgement.

Of course, the ability to summon was entirely inherited and no one who had it got a choice about it, so entire families were destroyed centuries ago after the initial declaration by the church. However, some summoners survived, and their powers lingered on as they hid them from the world and continued to hide their children.

Unfortunately, unlike crests that need proper equipment to identify them, summoners had a physical mark somewhere on their bodies that identified their Eidolon, the being that they could summon. This meant they physically had to hide the mark, an impossible task for a baby.

"We should've told him."

His wife said those words with deep regret, regret he fully felt.

She was also a summoner, able to call upon Sylph, but that information had not been shared with their son. He hadn't been born with the ability, so they believed that if the worse happened, he would be genuinely ignorant of his mother's 'sin' and spared punishment. Sadly, this meant he bought into the church's doctrine and believed that summoning was evil, and they feared what he and his wife would do if they knew about Raphael's power.

"The illusion spell I've used is strong, and subtle, no one will notice it's there."

Her words pulled him from his thoughts, and he nodded, "At least that will give us time."

Sylph granted his wife illusion magic, and years of practice and necessity had made her skilled, she could create ongoing illusions that were hard for most mages to detect. However, it wasn't a permanent solution, any illusion she created will dissipate with her death, but they would hopefully get years to work things out before that happened.

He looked to her once more, "Do you know which Eidolon he has?"

"I'm planning on looking into it."

31st of the Verdant Rain Moon, Imperial Year 1161

A Duscur mother cradled her new-born baby, smiling down at him softly. The boy shifted and grumbled, revealing the mark on the right of his chest, just below his neck.

Her husband had already identified it as Diablos, a powerful Aeon for a Scion to have.

In Duscur, those the people in Fόdlan call summoners are known as Scions, and Eidolons are called Aeons. In the past, Scions were respected and revered, people believing them to have been granted favour from one of their gods and given their Aeon to help them. However, one group of Scions became filled with greed and the war they waged devastated the country. Since then, Scions became deeply mistrusted and feared, most communities casting them out, believing them to be omens of doom and misfortune. Though it was better than Fόdlan's outright hostility and fatal condemnation, they still found it better to hide their gifts.

However, these thoughts didn't trouble the young woman, her husband was highly knowledgeable about Aeons, coming from a long line of Scions himself. His though was Faerie, an Aeon skilled at healing magic, so the more complex Diablos would be a different challenge, but his family had long kept records of various Aeons.

She looked towards the future in hope, Dedue was a strong baby and she was certain that he would master the powers given to him by Diablos, complex as they were.

She hummed gently, rocking the boy gently as he settled, not even twitching as his father came in from the forge.

He'd dropped everything when she'd gone into labour, rushing to her side and abandoning his work. He'd spent the quiet after the birth tidying and shutting down the forge as she fed and settled their son. Now though, he softly approached and placed a gentle hand on her shoulder.

"He's already asleep?"

She nodded gently, "Yes, he dropped off as soon as he was done eating."

He lowered himself into the only other chair in their small home, near the fire, "I looked into the kind of magic he'll have."

She looked at him in interest, each Aeon granted only a certain selection of magic, though the size of the selection varied, and while he remembered that Diablos' magic was complex, he didn't fully remember what type it was.

"Apparently Diablos is a master of Space-Time magic."

Her eyebrows shot up, Space-Time magic was very complex and rare, they only knew it existed because of old Scion tales and records. To think that her son had access to such a rare magic.

Her husband grinned, "I know, I barely believed it myself, but Faerie assures me that's the case."

An Aeon could converse inside the mind of their Scion, even if they weren't currently summoned, and her husband often said that Faerie was very talkative.

She looked down at her sleeping child, "Is there something coming, why would our son be given such a magic."

"I don't know." He smiled again, "But there's no use worrying over it now. We don't need to trouble him until he's older."

He had a point, it would be a few years at least before Dedue would even be able to summon Diablos, they would wait until his sixth birthday for that, and even longer before he would be able to do any really powerful magic. For now, they could just enjoy having their new son.

Dedue grumbled and shifted again, and she carefully tucked the blanket wrapped around him in a bit, covering the mark once more.

"One day little one, you're going to be a better Scion than even your father."

"Hey!"

Her husband gave a soft cry of pretend indignation, but she simply smiled, and he shook his head, "Just because Faerie doesn't have a single aggressive spell to her name."

"And there's nothing wrong with that." She assured him, "I just meant our son would be better because he would have an amazing teacher."

He gave a soft laugh, "I love you."

He carefully came over and gently stroked Dedue's head, "And I love him too."

PS-So, a long intro to set up the way things work and the world's view of their powers. Please let me know what you thought.