That step Vance took backward? Regulus didn't dwell on it. The whole thing had been a performance duel, nothing more.
He hadn't used anything beyond the second-year syllabus. Not a single spell outside what they'd been taught.
Vance had held back too. No professor was going to go all-out against a twelve-year-old. And beyond the basic curriculum, the deadlier, more efficient techniques the man had ground into his reflexes through real combat... none of those had come out either.
For Vance, the aftermath would probably amount to a passing remark over lunch. Something to Professor Flitwick like:
"The Black boy in second year. Not bad. Made me use a Shield Charm."
Flitwick would nod and say, "He does have a remarkable gift."
Slughorn, if he overheard, would slide over with that warm smile. "That child has always been exceptional."
McGonagall, if present, would probably just hum once.
That kind of reaction. Nothing more.
Of course, among the younger students, forcing a professor to use Protego and driving him back a step was sensational. The story would spread. Lower years would treat it as legend. But the older students? They'd hear it and move on.
A professor fighting an exhibition match against a second-year, clearly pulling his punches. What was there to get excited about?
Was Black strong?
Strong. Everyone agreed on that.
But by the time the story traveled from the lower years to the upper, it would already be warped. In the ears of the senior students from other houses, it would boil down to: that Slytherin Black showing off again.
Nobody would take it as a serious measure of anything.
So the incident would pass, leaving behind a few extra whispers among the younger students and a marginal bump in reputation. Nothing more.
Regulus let it go. But something else had been turning in his mind.
Last term, in Defence Against the Dark Arts, Professor Merrythought had taught the Spark Charm. Red and green orbs of light from the tip of the wand.
He'd stared at that light, and several ideas had jumped loose.
Could light carry information? Could information itself become a weapon?
Or give light a physical form, charge it with energy, and detonate it.
Or invest it with symbolic meaning.
Light was warmth. A force against darkness. It illuminated, scattered fear, brought hope.
If magic could embody all of that, then light wasn't merely light. It was something more fundamental.
Where it touched, darkness retreated on its own.
Like what Dumbledore had done beneath the Astronomy Tower. A single beam of white light, and the grey fog dissolved.
Regulus suspected that might have been the meaning of light itself, with nothing else layered in.
Take it further, and light could also be the light of civilization.
Humanity learned to make fire in the dark. Light came first. Then civilization.
Wizards were probably no different.
The earliest among them had likely worked out the first spell sitting beside a campfire.
Light was wisdom. Enlightenment.
If a spell could fold every meaning of light into itself, it wouldn't merely illuminate. It would awaken.
Awaken the things buried inside people's minds.
At that point, it might stop being magic entirely.
Later, standing atop the Astronomy Tower and watching the moon, his thoughts had gone further still.
Compress light past the visible spectrum. Into ultraviolet. Into X-rays. Into gamma radiation.
It wouldn't hurt when it hit. No pain, no sensation. But atoms inside cells would have their electrons knocked loose, DNA chains would fracture, and days later the skin would start to ulcerate, organs would hemorrhage, and death would come without a sound.
Regulus knew the Muggle word for it: radiation. In the wizarding world, that was a curse.
Then there was destructive interference. Making light cancel itself out, letting you vanish inside the light around you.
Or turning light into a fuel source. Forcing atomic nuclei to fuse under extreme heat and pressure, releasing light that carried annihilating force. Wherever it struck, matter would cease to exist.
These ideas were too vast. So vast he couldn't see their edges, couldn't be sure magic could ever reach that far.
But the original notion, using light to carry information, that was worth pursuing.
In physics, light could carry information.
Light was a wave. Waves had three properties that could be varied: amplitude, frequency, and phase.
Adjust those, and you could encode information into light.
Muggles used fiber optics to transmit signals and electromagnetic waves to transmit images. The principle was always the same: encode information as a light signal, send it out, receive it, decode it.
A single thin glass fiber could carry more data in one second than every book in the Hogwarts Library combined.
The logic held.
But magic wasn't physics. Light's ability to carry information was one thing. Getting that information into a target's consciousness was another.
He couldn't shine a beam at someone and expect their brain to spontaneously conjure whatever image or thought he'd encoded.
There was a missing link. An input port for the information.
A wizard's brain had natural defenses. Chaos, ego, an instinctive rejection of foreign input.
To deliver a message that was specific, complex, and possibly coercive, he'd need a more direct method.
He thought of Legilimency.
---
Late at night. The Restricted Section.
Regulus stood before a shelf against the wall, his finger hovering an inch above the spines of the books, eyes closed. His magic reached out like invisible feelers, brushing against the thought-impressions preserved within the bindings.
References to Legilimency were scattered across several different texts.
He skimmed past the lengthy historical accounts and moral debates, hunting for the core descriptions.
Legilimency was a precision key. It opened the drawers of memory and leafed through their contents.
But there was a problem. It only extracted. It couldn't write.
Regulus withdrew his magic and opened his eyes.
Legilimency pulled things out. What he wanted to do was push things in. Opposite directions, but the underlying logic connected.
Pulling out meant forcing open another person's memories and locating the desired information.
Pushing in... would that mean disguising his own information as something that already existed in the target's memory? Slipping it past the gates?
Use light to deliver the information to the target's eyes. Let the target's brain receive it on its own.
There needed to be a conversion step. Turn the information into something the brain could recognize.
Legilimency extracted information and made the caster's own brain understand it, which meant the information was already being translated into a brain-readable format during extraction.
Reverse it, then. If he could translate the information he wanted to send into that same format, load it into light, and shine it into the target's eyes...
Would the target's brain, while processing the visual signal, mistake it for a thought it had generated itself?
That meant he needed two things.
First: a method to encode information into light. Second: a way to make the brain register it as I thought of this myself when the light was received.
Regulus stood in his corner of the Restricted Section and thought for a long time.
The encoding side, he had ideas for.
Control the color, the brightness, the rhythm. Break the information into segments and embed them in the light pattern.
The reception side had to rely on the target's own brain.
He didn't need to force information into anyone's head. He only needed the target's brain to automatically process the encoded light into something resembling a thought the moment they saw it.
This was the insight Legilimency had given him.
Legilimency could dig through another person's mind because it understood the rules by which brains processed information.
Reverse it. If he could map those rules, he could make the brain lie to itself.
The thought settled, and in its wake came a familiar calm.
The problem had been broken into concrete steps. The goal was clear. All that remained was solving them one by one.
He left the Restricted Section, Disillusionment Charm wrapped around him like a second skin, slipping through the empty corridors.
The halls were quiet. Only torchlight swayed against the walls.
What he needed to do first was prove that light could deliver information to someone's eyes.
Everything after that could come in time.
---
Friday night. The Room of Requirement.
From outside came the crack and hiss of Cuthbert and Alex sparring, punctuated now and then by the sharp whistle of Hermes's Dark Magic cutting through air.
Regulus sat in his private chamber, a sphere of light hovering before him.
Lumos.
Over the past two days, he'd completed the groundwork for the first and second phases.
Phase one was confirming the carrier. He'd chosen the Wand-Lighting Charm as the base spell for modification.
Not because it was powerful. It was the opposite of powerful.
Because it was the simplest, the most stable, its magical structure transparent and easy to reshape.
He needed a spell that could produce a steady beam of visible light while allowing precise control over the frequency, intensity, and flicker pattern.
He'd spent an afternoon dismantling it, rebuilding it, testing it, and arrived at an improved version.
It no longer produced a constant orb. Instead, the light obeyed his will, brightening and dimming in specific rhythms, shifting color, flowing.
That gave him a way to encode information into light.
Different colors mapped to different emotions. Different intensities to different magnitudes. Different rhythms to different logical sequences.
Light had become a carrier.
Phase two was preparing the information itself, something he could call up at will.
His first instinct had been to transmit a simple visual image or a verbal command, but converting abstract concepts into light signals was enormously complex.
He changed approach. He'd start with emotions and mental inclinations.
These were closer to the kind of content Legilimency operated on, and easier to perceive and verify.
He recalled the containment room he'd built deep in his consciousness when dealing with the Dark Awakening.
That room held a virtual personality saturated with dark contamination, serving as a minefield for his mental defenses.
His mind was stronger now than it had been then. He partitioned a new isolation zone.
Inside it, he stored a curated collection of extreme, distilled emotional samples, organized by type.
These emotions weren't drawn from his own experience. They were precision-synthesized through raw mental simulation.
Groundless self-confidence. Contempt aimed at a specific target. Recklessness amplified severalfold. Pure curiosity. Pure fear.
Each sample had been stripped of its original context, reduced to nothing but the core inclination itself.
Using willpower and mental discipline, he compressed each emotion into a stable structure. Like squeezing fog into stone. It sat there, inert, unchanging, incapable of leaking or drifting. When he needed one, he'd break off a piece.
The first two phases were complete. Now he had to bring them together, and solve the question of how to make the target's brain deceive itself.
Regulus began dissecting the mechanics of Legilimency.
The spell worked by constructing a channel of magic between caster and target, a mental corridor through which the caster's consciousness traveled to locate and seize memories.
He needed to reverse it.
He also needed a one-way channel from himself to the target, but it wouldn't carry probing magic. Only light, loaded with a specific emotional inclination.
That light couldn't merely shine on someone. It had to function like Legilimency's probe: recognizing the boundary of another mind, establishing a temporary connection, slipping past the shallow defenses.
Then releasing the embedded emotional inclination onto the surface of the target's consciousness. Staining it.
This initial version didn't need deep implantation. Didn't need lasting effects.
If he could prove that the target, upon contact with this specific light, experienced a brief corresponding emotional shift or mental inclination, that would count as success.
It required extracting the components of Legilimency responsible for mental targeting and connection, then nesting and fusing them with the modified Lumos.
How to align the magical nodes. How to make two fundamentally different types of magic coexist without canceling each other. How to ensure the information transferred intact in the instant the connection formed.
Problems piled on problems.
And then he hit a wall.