**Summer, 1967**
Regulus Black turned six in the summer.
In the House of Black, turning six meant graduating from the nursery to the attic. It was a rite of passage. You were no longer just a child; you were a scholar in training.
The attic of Number 12, Grimmauld Place, became Regulus's kingdom. It was dusty, smelling of dry rot and old parchment, but it was his.
He spent his first week sitting in the center of the room, asking a question that seemed to have eluded wizardkind for centuries.
*If wizards can heal broken bones in seconds, why are their bodies still so fragile?*
A simple *Stupefy* could knock a grown wizard unconscious. A fall from a broom could kill them. They wielded the power of gods, but they lived in bodies made of glass.
*Why has no one systematically studied the vessel?* Regulus wondered. *Magic flows through us like water through a pipe. If the pipe is rusted and thin, the water pressure bursts it. If the pipe is steel, surely the flow can be stronger?*
This was a blind spot for the civilization he had been born into. They treated the body as a suitcase for the soul—something to be carried around, not improved.
Regulus sat cross-legged on a velvet cushion. He closed his eyes and turned his attention inward.
He felt the magic. It was a hum in his blood, a warmth in his chest. The textbooks said magic originated in the soul and exited through the wand.
*Simple. Too simple.*
Regulus stood up and walked to the skylight. The autumn sun sliced through the grime on the glass, painting a bright square of light on the dusty floorboards. He stretched his hand into the beam, feeling the heat.
He closed his eyes again.
*Move,* he commanded.
He didn't use a spell. He didn't use a wand. He just used his will. He tried to push the hum in his chest down his arm, toward his fingertips.
It was like trying to herd cats. The magic resisted. It wanted to stay in its natural equilibrium. It felt sluggish, heavy.
But Regulus had something most six-year-olds lacked: the patience of an adult who had lived a life before this one.
He imagined his will as a shovel, digging a trench. He imagined the magic as water filling it. Drop by drop. Inch by inch.
Two and a half hours later, sweat dripping down his back, he felt it.
His right arm didn't just feel warm from the sun. It felt *full*. It buzzed with a static charge. He clenched his fist. The muscles felt tighter, denser. He punched the air. It was faster.
*It works,* he thought, exhaling a breath he didn't know he was holding. *The vessel can be filled.*
◈ ◈ ◈
Over the next few days, Regulus became a ghost in his own house. He watched his family not as relatives, but as test subjects.
Walburga was his first subject.
Her magic was explosive. When she screamed at Kreacher, the curtains shook. But Regulus watched closely. After she cast a complex protective ward over the fireplace, she would unconsciously rub her temples. Her face would go pale for a split second.
*Magical exhaustion is physical,* Regulus noted. *The body bears the load. She has power, but no stamina.*
Next was Orion.
His father's magic was deep, like a still ocean. His control was absolute. But when he spent hours in the study casting detection charms on Ministry documents, his fingers would tremble when he picked up his tea.
*Fatigue,* Regulus noted. *Muscle tremors. The nerves are frying under the current.*
And then there was Sirius.
Sirius was in the garden, trying to impress himself. He was levitating pebbles, trying to arrange them into the constellation of Canis Major.
"Get... up!" Sirius grunted, his face red.
The stones wobbled into place, hung there for three seconds, and then clattered down.
Sirius collapsed onto the grass, panting as if he had run a mile. He wiped sweat from his forehead with a dirty sleeve. "I'm... exhausted."
Regulus walked over, holding a glass of water.
"Did that use a lot of energy?" Regulus asked quietly.
Sirius snatched the glass and downed it in one gulp. He nodded, too out of breath to speak. He didn't look at Regulus. The memory of their argument at dinner still hung between them like a curtain.
Regulus took the empty glass back. *Evidence conclusive,* he thought. *The bottleneck is the body.*
He turned and walked back to the house, leaving his brother panting on the lawn.
◈ ◈ ◈
A week later, late at night.
The study was dim, lit only by a single silver candlestick. Orion looked tired. The shadows under his eyes were deep. The Ministry was in chaos—whispers of attacks, disappearances, the dark mark appearing in the sky.
"Come in," Orion said, not looking up from his parchment.
Regulus slipped inside and sat in the high-backed chair opposite the desk.
"Father," Regulus said.
"Speak," Orion sighed, rubbing his forehead. "What is it?"
"I have a question," Regulus said. "Where exactly is magic stored?"
Orion paused. He looked up, blinking. "That is a basic question. Magic originates from the soul and manifests through the body."
"But the body isn't just a door, is it?" Regulus pressed. "If the body is damaged, casting is harder. If the body is strengthened... would the capacity for magic increase?"
Orion frowned. "Theoretically, yes. A healthy wizard casts better than a sick one. But beyond basic health, the consensus is that physical conditioning has negligible returns."
"Has anyone tested it?"
"The traditional view," Orion said, leaning back, "is that magical power is fixed at birth. You can improve your aim, but you cannot increase the ammunition."
"But what if the ammunition is limited by the size of the gun?" Regulus leaned forward. "Like a glass. If the glass can only hold one cup of water, pouring more in just makes a mess. But if we make the glass bigger..."
"The soul is the cup," Orion interrupted. "Not the body."
"Are you sure?" Regulus asked softly.
Orion stared at him. The silence stretched.
"I am not sure," Orion admitted slowly. "But it is the accepted theory."
"Accepted does not mean correct," Regulus said. "It was accepted that the earth was the center of the universe. It was accepted that Muggles were monkeys. Both were wrong."
"Enough," Orion warned, though his voice lacked heat. "Regulus, you are clever. But you are asking questions that do not have safe answers."
"When should I ask them?" Regulus challenged. "When Lord Voldemort knocks on our door?"
Orion stood up so fast his chair scraped loudly against the floorboards.
"Who told you that name?" His voice was dangerous.
"No one," Regulus said calmly. "I listen. Cousin Bella whispers it. Mrs. Malfoy whispers it. You whisper it."
Regulus looked his father in the eye. "Tom Marvolo Riddle. He calls himself Lord Voldemort. I know."
Orion sank back into his chair. He looked suddenly very old. "You should not know these things."
"But I do," Regulus said. "He is recruiting. The families are picking sides. We will have to choose. I am not scared, Father. But I need power. If the traditional way isn't enough, I need to find a new way."
Orion closed his eyes. He sat there for a long time, listening to the crackle of the fire.
"You ask about the body," Orion said finally, his voice low. "There was... one. An ancestor. My great-grandfather, Arcturus Black the Second. He believed as you do. He thought wizards were arrogant, neglecting the vessel for the spark."
Regulus held his breath. *A precedent.*
"He conducted experiments," Orion said grimly. "He used magic to reinforce his bones, his muscles, his organs. He created a cycle—strengthen the body to hold more magic, use more magic to strengthen the body."
"And?" Regulus asked, leaning forward.
"He lived to be 137," Orion said. "He was incredibly powerful. He could crush a stone with his bare hand and cast spells that would exhaust three normal men."
"But?"
"But he went mad," Orion whispered. "In his final years, his journals turned into gibberish. The last entry he wrote was clear, though. *'The container is too sturdy. The contents cannot get out. I have trapped myself.'*"
Regulus felt a chill. *Trapped?*
"What does that mean?"
"I don't know," Orion said. "His notes are sealed in the Restricted Section. I tried to read them once. I got three pages in and nearly passed out from the headache. They are cursed, Regulus. Or just... wrong."
"I want to see them."
"No." Orion's refusal was instant. "Not now. Perhaps never. Arcturus's end... it was not dignified."
Orion leaned over the desk, his eyes intense. "Promise me, Regulus. Promise me you will not go looking for those notes on your own."
Regulus looked at the flickering candle. He didn't want to lie. But he couldn't stop.
"Promise me," Orion repeated. There was a pleading note in his voice.
"...I promise," Regulus lied.
Orion sighed. He knew it was a lie. But he accepted it because he was too tired to fight it. "Go to bed."
Regulus climbed back up to the attic. He sat in the dark, listening to the wind rattle the skylight.
*Arcturus Black. 137 years old. Insane.*
*The container is too sturdy.*
Regulus looked at his hand in the moonlight.
*If the body becomes a cage, the soul suffocates,* he theorized. *But what if they weren't separate? What if I didn't just build a better container? What if I fused them?*
He closed his eyes and began to push the magic through his arm again.
*I won't make your mistake, Grandfather,* he thought. *I won't build a cage. I'll build a fortress.*