The year before Hogwarts was not idleness.
Cassius did not know idleness.
His tenth winter bled into spring, and instead of losing momentum he only sharpened further.
The Arcanum was no longer merely a shadow society—it was a machine.
Its gears spun day and night, fed by coin, intellect, and Cassius' endless stream of ideas.
Hogwarts would come.
The letter would arrive near his birthday, gilded with tradition, heavy with expectations.
But Cassius knew that once he stepped into those halls, he would be hemmed in by their rules and their eyes.
So this last year was freedom.And he would use every second of it.
The diadem sat cold upon his brow, whispering clarity into the folds of his thoughts.
Every time he wore it, the chaos of his mind ordered itself into blueprints and schematics, into polished theories instead of tangled webs.
He used it sparingly.
Not out of fear of corruption—it had no dark magic to it since the diadem never became a horcrux—but because the brilliance it granted him came with cost, which was the slowdown of gained experience to his thinking skill when he studied on his own, thankfully idle slots could still gain experience regularly.
The diadem was just one of his many tools, one he would continue to use until his own skill level reach the same mark or even surpassed it.
The first great project of his: broomcraft.
The Nimbus 2000 had not yet been invented.
The Firebolt was still a dream.
The Firebolt Supreme—decades away.
Cassius would not wait.
He was determined to make an overwhelming presence within the school and what better way to do that than have his own custom build flying broom far surpassing the competition, making him become the greatest seeker in the world, far outshining the meager natural talent of his twin.
He sketched new flight-stabilization charms, balancing matrices that would eliminate the clumsy wobble of older brooms.
He theorized about the perfect wood to be used for the future Aeriusbolt, deciding upon Ebony thanks to the woods light weight but hard nature.
When treated properly the wood could become harder than steel, rivaling the diamond-hard claim for the Firebolt.
While the broom itself would be a combination of Birch and Hazel twigs to give the creation ample power, and swift turning.
With the directive set the Arcanum began to move on his whims rushing to assemble the single fastest broom the world was most likely ever to see.
When Hogwarts opened its skies to Quidditch next year, Cassius planned to arrive with something faster, sleeker, deadlier than anything the world had ever seen, but only after proving himself vastly superior even to older students during his 'first' flying lesson.
~
Another problem gnawed at him late into the night: the Patronus.
Ancient, yes.
Powerful, certainly.
But why so limited?
Why only a silver animal, often fixed for life?
The diadem whispered possibilities.
A few rare patronus's could change into magical creatures so what was the requiremnet?
And if a patronus could change, could an animaguys as well become a magical animagus?
Could a witch's otter instead become an Erumpent, a Thunderbird, a dragon?
Cassius drew parallels between the two arts: Patronus could be counted as conjuration and Animagus transfiguration.
Both required intent, identity, self-knowledge.
Perhaps the boundary between them was thinner than scholars believed.
And then the thought struck harder still:
What if there could be the opposite of an Obscurus?
A light-fed parasite, born not from repression and pain, but from overflowing joy and purpose?
A luminous twin to the shadow parasite, one that enhanced its host instead of destroying them?
Cassius named it in his notes: The Lucidus.
A parasite that enlightened rather than obscuring a witch or wizards future.
The Arcanum gaped when he presented it, but they obeyed.
Experiments began at once, of course only on volunteers but those were readily available thanks to the muggle corporations efforts to expand Cassius's reach.
Thankfully the research fell on the light side not dark, saving them from having the ministry come crashing down on them preventing the project from getting off the ground.
From there his mind leapt again.
If curses were only magic twisted toward cruelty, could they not be rewritten?
Forgiven?
The Killing Curse became, in theory, the Living Charm.
A spell that could prevent death even if one wanted it, perhaps a worse curse than the instant death with no pain.The Cruciatus became the Comfort Charm, forcing not pain but bliss, bringing about the purest form of comfort quickly dispelling maledies of the mind, and body, undoing traumas as if they had never occured to begin with.The Imperius became the Freewill Charm, flooding the victim not with subjugation but with clarity, releasing them from fear, or outside manipulation allow them to be free in the truest sense of the word.
It was wild thinking.
Dangerous even.
And yet, even a failure taught more than standing still.
~
The next problem was practical.
The magical world resisted technology like oil resisting mixing with water.
Radios were the most advanced technology not due to lack of trying.
When Televisions and computers were brought into the Arcanum for testing, they simply didnt power on, even if they could images wouldnt display and components failed to operate.
The explanation was interference, ambient magic disrupting delicate circuitry.
Cassius did not accept that.
In the Muggle world, his corporations had already outpaced their decade.
Privatized spaceflight going on extraplanitary journeys to begin acquisition of new materials.
Early AI already in the works.
But none of it could yet cross into the wizarding world.
So Cassius ordered new lines of research: magical insulation, adaptive rune-circuits, hybrid engines that ran on both electricity and spell-energy.
He imagined a world where a wizard could carry a laptop in Hogsmeade, or where enchanted rockets pierced magical skies without sputtering into failure.
Equally so was to bring Muggle weapons into the magical world to increase the protectiveness of the simple Shield charm such that magic could quite literally stop a bullet, rather than succumb easily once the two worlds were merged back together once more.
It was no longer about convenience.It was about dominion.
If he could merge the worlds, then neither could resist him.
~
Money, he had decided, was no longer enough.
Gold bought him silence.
Influence.
But it did not topple a Minister, bending him to his will.
So Cassius shifted tactics.
Through proxies, he unleashed Rita Skeeter upon Cornelius Fudge.
Page after page dripped poison into the public ear: Fudge's incompetence, his cowardice, his reliance on Dolores Umbridge to do his dirty work.
Every slip, every hesitation, every botched response was magnified and ridiculed.
The Daily Prophet began to turn.
Fudge was mocked in cartoons, criticized in op-eds, whispered about in pubs.
Even his allies grew uneasy.
Dumbledore, of course, watched.
The old man would see the strings, would know some shadow was pulling events.
But even he could not trace them back to "Arcana."
Not yet.
By spring, Fudge still sat in his office—but his throne was cracked.
And when Voldemort inevitably rose again, as Dumbledore insisted he would, the crack would shatter.
~
Summer loomed.
Cassius would turn eleven, and the letter would come.
His last months of freedom he spent balancing ruthlessness with restraint.
His magic almost completly stabalized within.
He let the Arcanum run on momentum, intervening only to correct course, or inject new ideas as the came to him.
At night, he sometimes allowed himself to imagine Hogwarts.
The Sorting Hat upon his head.
The gasps of professors when his name was called.
The quiet rage in Dumbledore's eyes.
The confusion in Severus'.
Would he reveal the truth of his lineage immediately?
Or wait, letting suspicion stew until the reveal struck hardest?
He smiled at the thought.
Timing, as always, was everything.
Until then, he waited.
Not idly, never idly.
But with the patience of a spider at the center of its web.
When the letter came, Hogwarts would no longer be a sanctuary of learning.
It would be his playground.