Back in his room, Regulus shut the door and went to the window.
A few Muggles passed along the street beyond the square, hurrying even on Easter, always somewhere to be.
His father's words echoed in his head.
The lines had been drawn long ago. The House of Black stood publicly with Voldemort. Every pure-blood family in Britain knew it.
Switching sides now meant open betrayal, and Voldemort's stance on betrayal was something no one in the wizarding world misunderstood.
Regulus didn't need to study Voldemort closely. He only needed to look at the evidence.
The wizards who had vanished. The Ministry of Magic officials who'd reversed their positions overnight. The dissenters who had simply ceased to exist.
At the core of how Voldemort built his authority was a single, non-negotiable clause: disloyalty would not be tolerated.
Gone was the leniency of his early recruitment days. What he showed now, more and more openly, was his true face.
Cruelty had become routine, violence a tool, absolute obedience an iron law settling into place. Dissent suffocated before it could draw breath. The more terrifying his displays of strength, the more feverish his followers' devotion grew.
This version of Voldemort was more popular among the pure-blood circles than ever. He represented what most of those families wanted.
He was no longer merely an option. He was becoming the sharpest blade of the pure-blood collective will, cutting down opposition, cementing privilege, purging bloodlines.
Their order didn't tolerate betrayal either. And Voldemort was that order's most violent enforcer.
Besides, magic was power.
In the end, everything circled back to the oldest and most unanswerable law of all.
If the House of Black turned now, for any reason, Voldemort wouldn't allow it.
Even if it were only to make an example for the other pure-blood families. Even if it were only to uphold the principle that rules couldn't be broken. The Blacks would face destruction.
So until he truly possessed the power to choose freely, he couldn't show a single sign.
Regulus thought about the Hogwarts professors.
The shift this school year had been obvious, or more precisely, it had begun after his Patronus was exposed during the Astronomy Tower incident.
The Patronus had acted like some kind of credential. Once it appeared, something changed in the way Dumbledore looked at him.
But Regulus knew himself. A Patronus didn't represent all of him. It was a reflection of one facet of his soul.
He could stand beneath that spiraling silver light, perfectly calm, and articulate every syllable of the Killing Curse. Watch green light bloom at his wand tip.
He thought again about what Dumbledore had said: that Fawkes seemed interested in him. Phoenixes could see souls, drawn to what was pure and warm.
Whether it was the phoenix that had seen something, or Dumbledore projecting his own perception, Regulus couldn't be sure.
Either way, the Headmaster's regard was translating into tangible advantage.
The professors' instruction happened behind closed doors. The most Voldemort could learn was that the younger Black son was studious, asked good questions, and his teachers were fond of him.
Voldemort might even approve. A boy who was outwardly humble, handsome, brilliantly talented, beloved by his professors. Like a younger version of himself.
But when someone like Voldemort saw another person who resembled him... what would he think?
Regulus frowned.
While he was still weak, Voldemort might appreciate him. See potential worth cultivating.
But once he grew strong enough to register as a threat?
A person who mirrored the Dark Lord. Equally distinguished lineage. Equally exceptional talent. Equally valued by his teachers. Equally clear about what he wanted.
What would Voldemort think then?
He's too much like me. Why would he ever be content as a follower?
The answer probably wasn't pleasant.
Then again, Voldemort was proud. The kind of pride that came from wielding overwhelming power, from standing at the apex of the wizarding world, from the unshakeable conviction that he had surpassed every witch and wizard alive.
Proud people tended to look up, or straight ahead. Rarely down.
Regulus wasn't yet high enough to cross that downward line of sight.
The real question was: what kind of power would give him the freedom to choose?
He didn't know the exact threshold. There was no catching up to Voldemort's decades of accumulated magic in a short span, let alone Dumbledore's century of depth.
His talent was formidable, yes. But Voldemort's and Dumbledore's talent was equally formidable, perhaps more so, because they'd already proven how far it could take them.
Until he had that kind of power, nothing would change. The family's position wouldn't change. Voldemort's expectations wouldn't change. The state of the wizarding world wouldn't change.
Regulus shook his head, pushing the thoughts aside. He crossed to his desk, sat down, and pulled open the drawer, retrieving a notebook he'd taken from the family library.
No name on the cover, but the handwriting and phrasing marked it as the work of some Black ancestor, likely from the seventeenth or eighteenth century.
He opened it. Inside was a single spell.
Fiendfyre.
His fingers brushed the page, feeling the characters written in enchanted ink.
Time had caused the ink to bleed slightly at the edges, but the magical imprint remained sharp. He could sense the emotions and power the writer had poured into every stroke.
He read page by page.
Fiendfyre. One of the most dangerous pieces of dark magic in existence.
At its core, it was cursed fire with a will of its own. No fixed incantation. No elaborate preparation required. It was summoned directly through the caster's magic and intent.
The flames defaulted to an orange-red, but their temperature and properties bore no resemblance to ordinary fire.
Devastatingly destructive. Temperatures far exceeding normal flame. Capable of incinerating magical objects and structures.
But Regulus knew it went further than that. Fiendfyre could destroy Horcruxes. In the original story, it was the only dark magic explicitly recorded as capable of doing so. Ravenclaw's diadem had been destroyed by Fiendfyre that spiraled out of control.
He read on.
The fire possessed self-awareness. It would spontaneously assume the forms of dragons, serpents, chimeras, and other predatory creatures, actively hunting living targets rather than burning passively.
It fed on whatever fuel it found, growing stronger the longer it burned.
It could not be extinguished. Standard counterspells like Aguamenti were useless. Only the complete exhaustion of fuel or the caster's death would cause it to die out. No known direct counter-curse existed.
The risk of backlash was extreme. If the caster's control faltered, the flames would consume them first.
Regulus's mind jumped to Vincent Crabbe, lost control, and perished in his own fire.
That Slytherin student from the original story. Regulus had met his father, Crabbe, at the Malfoy family's Christmas banquet.
Looked at from another angle, though, Vincent Crabbe had accomplished something significant. He'd accidentally destroyed one of Voldemort's Horcruxes without ever knowing it.
What separated Fiendfyre from conventional fire magic was the curse element.
A standard Incendio was controllable, limited in power, and would die the moment the caster stopped feeding it magic.
Fiendfyre, once ignited, broke free of the caster's initial command and became an independent engine of destruction. It belonged to the domain of high-level elemental dark magic.
Starting a Fiendfyre was easy. With enough raw power and vicious enough intent, anyone could light one. Making it obey... that was another matter entirely.
Regulus turned the page. The notebook laid out the hard prerequisites.
Magical reserves needed to exceed the level of a mature adult wizard, far beyond what Hogwarts NEWT examinations demanded.
A foundation in dark magic theory was essential. The caster had to understand the principles of curses and the binding mechanism between curse and element. Knowing the words wasn't enough. You had to grasp the logic behind them.
He measured himself against the criteria. On the magical reserves front, months of meditation had refined his power. His total capacity and recovery rate already surpassed most adult wizards.
Dark magic theory... he'd consumed volumes of it. That should suffice.
Further in came the training steps.
Step one: emotional anchoring.
Intense negative emotion served as the fire's fuel. Hatred, the desire to destroy, killing intent.
Practice was to take place in a secure, sealed environment, a fireproof magical training chamber with nothing combustible, repeatedly synchronizing emotion and magical output.
At this stage, no actual flame was to be summoned. The goal was learning to convert emotion into a magical state primed for ignition.
His finger paused on this passage.
Negative emotion. He didn't harbor any particular, burning hatred. There was no one he needed to kill.
Destructive urges and killing intent were even further removed from his nature. But the notebook clarified: emotion was the fuel, not the control mechanism.
Ignition required darkness. Control required absolute calm.
Step two: form testing.
Begin with the weakest possible flame. Use willpower to constrain its shape, keeping it as a simple fire, preventing it from morphing into a predatory form.
This stage required continuous injection of magic to prevent the fire from expanding on its own. The moment control felt like it was slipping, terminate immediately with Finite Incantatem.
A note had been scrawled in the margin beside this section: Nine out of ten learners die at this step. Either their magic runs dry and the fire turns on them, or their will wavers and the fire swallows them whole.
Step three: controlled summoning.
Gradually increase the fire's intensity. Attempt to guide it into a single form, such as a small serpent, and issue simple commands, like burning in a circle.
If it failed, evacuate immediately. Don't try to salvage the situation.
On the subject of evacuation, the notebook was blunt.
The only reliable emergency response was to get out. Fiendfyre spread at terrifying speed. The caster needed to clear the burn radius immediately, with no attempt to stand and fight.
Alternatively, terrain could be used for isolation. If instant escape wasn't possible, redirect the fire toward an area with nothing to burn, stone clearings or zones behind magical barriers, buying time to flee.
But the fire would navigate around obstacles on its own, hunting its target.
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