Arthur stood in front of the containment chamber, the Mind Stone floating gently in front of him, and considered the path that had brought him here.
Weeks had passed since the night he had pulled the Scepter apart. The research was done. The experimentation was done. He understood, now, how the Mind Stone worked, and how Pietro and Wanda had gained their powers in the canon he half-remembered.
Now it was time to test those calculated results on the only human subject he was willing to risk.
Himself.
He was confident it would work. He had solid data. He had proven results. And he had a story worth remembering.
—
The very first test subject had been the standard white lab mouse. Winky had procured a large batch from somewhere. Arthur had not asked. He never asked. Winky simply got what he needed exactly when he needed it.
The Mind Stone, Arthur had discovered very quickly, was nothing like the other two Stones he had worked with.
The Power Stone had been cooperative in its own brutal way. Arthur had siphoned a fraction of its energy into a prepared crystal and used the crystal safely for controlled experimentation. The process had been delicate but predictable. Energy in, energy stored, energy channelled.
The Mind Stone refused the equivalent procedure entirely. The crystal he prepared simply expelled all of its absorbed energy within seconds, going dark and dead in his palm. He tried three times. Three complete failures. The Stone would not be split. It would not be bottled. It would not be used like a simple battery.
It was, Arthur realised, almost certainly conscious. And it had opinions.
That distinct impression deepened when he brought the first mouse near it.
Nothing happened.
The Stone did not react. No glow. No pulse. No activity of any kind. It was as if the Stone had looked at the tiny mouse, found it completely uninteresting, and flatly refused to engage.
Arthur spent a long evening adjusting parameters, recalibrating the containment field, and trying different distances and exposure angles. Nothing worked. The Stone ignored every single mouse he presented to it with the serene indifference of a cosmic being that had existed since before the formation of the first star and could not be bothered with rodents.
Eventually, Arthur tried a much less subtle approach. He placed every remaining mouse into a sealed enclosure together with the Stone, hoping that sheer proximity and numbers might provoke a response.
It did. But not the one he wanted.
The Stone remained inert as the mice scurried around inside the glass enclosure. Then, one of them accidentally brushed directly against its glowing surface.
A clean, violent pulse of yellow light erupted. It was contained inside the glass but powerful enough to vibrate the reinforced walls of the workshop. Every single mouse dropped completely dead where it stood.
Eve reviewed the resulting data. The pattern was unambiguous. The Stone had not killed them through physical force. It had reached into each of their minds and burned them out, all at once, with the cold efficiency of a man swatting flies that had finally annoyed him into action.
Arthur stood in front of the silent enclosure for a very long time afterward.
He had his first piece of useful information. The Mind Stone was not a tool. It had distinct preferences. It chose its subjects. It did not work on what bored it. And what bored it, it could destroy without the slightest effort.
Rats and mice were completely beneath its attention. Arthur needed to think bigger.
—
Arthur went directly to the chimpanzees.
He skipped every planned intermediate trial. There was absolutely no point in testing the Stone on animals it had already demonstrated contempt for.
He knew he might fail again. But he needed one successful, verified test before he could ever use the Stone on himself. He could not really risk his life the way he had at eighteen, when the Tesseract had nearly killed him. He had been a lone, desperate young wizard then, with nothing to lose but his own future. He was a vastly different man now. He had a wife. He had four children. He had a beautiful life he loved more than he had ever expected to love anything, and he had no intention of throwing it away.
So a chimpanzee became the final hope. If it worked, he would proceed. If not, he would likely scrap the enhancement project completely. Without a successful animal test, he was absolutely not risking direct human trials.
Winky procured several chimpanzees. Arthur, as always, did not ask from where.
He brought them into the containment room one at a time.
The first chimpanzee looked around the workshop, played happily with a metal bench leg, and was ignored by the Stone entirely. The second received the exact same silent treatment. The third, fourth, and fifth passed through the chamber without the Stone so much as flickering a single time.
Arthur was beginning to wonder whether he had built his entire research programme around a Stone that simply refused to cooperate, when the sixth chimpanzee walked in.
The Stone reacted instantly.
It emitted a slow, warm glow. It was significantly gentler than the violent pulse that had killed the mice. It was patient. Almost tender. It was as if the Stone had finally found something worth its vast attention and was taking proper care not to break it.
There was a quiet flare of brilliant yellow light. The chimpanzee slid softly to the floor, unconscious.
Eve showed Arthur the readings. The change was exclusively in the brain. Neural architecture restructured. Cognitive pathways expanded. Everything else, muscle, bone, organ, blood, was completely untouched.
The Stone worked on minds. Only minds. It had found a mind worth working on, and it had upgraded it.
The chimpanzee woke up exactly an hour later.
The very first look it gave Arthur was what changed everything.
It was not the look of a chimpanzee. There was meaning behind the eyes. There was consideration. Arthur had spent enough of his life around intelligent magical creatures. Fawkes, the giant squid at Hogwarts, and even magical snakes, to know what animal intelligence looked like. This was not that.
This was a person looking at him from inside a chimpanzee's skull.
—
Arthur spent the next seven days testing the chimpanzee.
He started with simple things. Shape sorting. Object permanence. Picture matching. The chimpanzee passed each test within minutes of being shown what was expected. Arthur made the tests harder. The chimpanzee passed those too.
By the second day, it was solving complex puzzles.
It was somewhere around the third day, watching the chimpanzee unhook a complicated latch he had assumed was beyond it, that Arthur sighed and gave it a name.
Caesar.
He named it after a particularly memorable chimpanzee from a science fiction novel he had read as a teenager. The reference was, he admitted to himself, not subtle.
Caesar appeared to genuinely like the name.
By the fifth day, Caesar was using tools. Taking things apart with deliberate intent. Learning to operate the spare holographic tablet in the lab the way a human toddler learns a smartphone. He learned through touch, repetition, and an intuition that vastly outpaced any instruction Arthur could give.
Through all of it, Arthur watched closely for what he was actually testing for. He looked for any sign of superhuman physical ability. Any latent gift the Mind Stone might have unlocked, the way it would eventually unlock blinding speed in Pietro or Chaos Magic in Wanda.
There was absolutely none.
Caesar's body was just a chimpanzee's body. His reflexes were a chimpanzee's reflexes. His physical strength was perhaps marginally higher than an average baseline, but well within the natural range.
The only thing the Stone had given him was a mind. And in a chimpanzee, evidently, that was enough.
For a chimpanzee, human intelligence itself was the superpower.
On the seventh morning, Arthur went down to the containment room and saw Caesar watching him quietly through the bars.
The chimpanzee was sitting perfectly still. His hairy hands were folded neatly in his lap. His head was slightly tilted. And in his dark eyes was something Arthur had sincerely hoped not to see.
Patience. The specific, chilling kind of patience that calculated future moves.
Arthur had absolutely no intention of birthing the Chimp equivalent of Ultron here in his own basement. He had no intention of letting the world of this MCU find out whether 'Rise of the Planet of the Apes' could be made real.
He made his cold, pragmatic decision.
Winky was at the workshop door when he came out.
"He was a good one, Master."
"I know, Winky."
"Master did the right thing."
"I know."
She closed the door behind her.
Arthur stood alone in the empty workshop for some time. Then he closed the digital case file permanently.
The principle was confirmed. The Stone enhanced minds, and from a better mind, everything possible to a given body would follow. Caesar's body had only been a chimpanzee's body, and so the only thing the Stone could give him was the only thing that body could carry. Awareness. Intelligence. A self.
—
Now it was his turn.
He had not told Eileen or the children. There was no need to worry them. He was confident that even if something unexpected happened, he would come out of it intact. He had the data. He had the test results. This was not the reckless gamble of a young wizard with nothing to lose. This was a calculated step by a man who had taken many calculated steps before.
In the containment chamber, Arthur looked at the glowing yellow stone floating in front of him and mentally willed it to activate. He knew it would work, and it did.
The Stone had responded immediately.
The jewel lit up blindingly bright, and the warm yellow glow covered him completely. The light felt distinctly conscious. It moved deliberately through his body, searching, analyzing every single cell, until it finally reached his mind.
Arthur felt the heavy light gather there. Then, with a precision that was almost tender, it began to work.
Arthur felt it happen in real-time. It was not a sudden flash. It was not a violent surge. It was like a deepening. Like standing in a room he had lived in for decades and discovering, in the space of a breath, that the ceiling was ten times higher than he had ever realised.
His core thoughts did not change. They simply expanded. The speed at which he could process information doubled, then doubled again. The number of independent ideas he could hold in active focus climbed from a handful to dozens.
Three minutes passed. The Stone dimmed quietly and released him.
Arthur sat very still.
The world had not changed. His magic was the same. His chi was the same. His body was the same. But the mind that controlled all of it was operating at a level it had never, ever reached before.
He reached for a complex spell chain. It assembled flawlessly in a fraction of a second. Not because his magic had improved, but because the mind directing it could now think faster, hold more variables, and execute with a precision that his old cognitive ceiling had not allowed. He turned his Death Sight inward. The perception was sharper, not because the ability had changed, but because the brain interpreting its input could now process finer detail. Every skill he possessed, every technique he had mastered, was running through a better processor.
The pilot had been upgraded. Not the aircraft.
Arthur sat with that for a while. Then he did something he had not done in years.
He created a clone.
The copy shimmered into existence beside him. It looked at Arthur. Arthur looked at it. The clone, knowing exactly what Arthur wanted to test, opened a portal and stepped through without a word.
Arthur waited. He braced for the old noise. The fragmentation. The sensation of being a committee masquerading as a person, a room full of overlapping conversations drowning out his own voice.
Silence.
The clone's perceptions flowed into his awareness like a second instrument joining an orchestra. Clear. Distinct. Running alongside his own thoughts without interference. He could feel what the clone felt, see what it saw, and his own focus did not waver by a fraction.
Minutes later, the clone returned and reintegrated. The memories slotted into place without the old disorientation.
Arthur sat in the quiet workshop and considered the implications.
He had given up clones after the Mephisto merge because the bandwidth was not there. One mind could not run multiple instances without the noise becoming unmanageable to live with. That limitation had been real. It had been the reason he had given up using clones after Mephisto.
The Mind Stone had removed the limitation.
He did not plan to fragment himself again. There was no urgency anymore. But the door was open.
—
A few more days of careful testing confirmed what he already suspected. Every skill he possessed had improved, not because the skills themselves had changed, but because the mind directing them was faster, sharper, and more precise. His control of chi was better. His control of magic was better. His channelling of dimensional energy was smoother. Even Ancient Magic was easier to handle.
All downstream effects of a single upgrade to the one system that governed everything else.
Then, his hand went slowly to the small silver chain resting around his neck.
—
The unassuming pendant had been Ravenclaw's Diadem once.
He had cleansed it of Voldemort's Horcrux with basilisk venom in his second year at Hogwarts, reshaped it from a crown into an unassuming piece of jewellery, and worn it almost every single day since.
Twenty-three years.
He activated it. Reached for the familiar boost. The expansion of cognitive capacity that had carried him through Hogwarts, through Kamar-Taj, through the Asgardian Archives, through wars against dark lords and demons and gods.
Nothing.
The enchantment was intact. The magic was strong. The Diadem worked perfectly. But Arthur's mind was so far beyond what the Diadem could enhance that he felt no boost at all. It was like holding a candle in front of the sun.
Arthur held the pendant in his open palm for a long time.
Without it, the man sitting in this underground workshop would simply not exist. Without the accelerated learning it provided, he might not have survived Hogwarts against all odds, much less the brutal wars against dark lords and gods. Without this object, every single thing he had built in this life would have taken twice as long or never happened at all.
Every great journey starts with a single step. Some journeys start with a tool that makes the first thousand steps possible.
This had been his.
"Thank you," he said quietly.
He carried it to the small mahogany case on the workshop's rear shelf. The one where he kept the things that no longer served him but had earned their rest. His first wand lay inside, Elder and Thestral hair, retired the day he had merged with the Hallows.
He laid the pendant inside, next to the wand. Closed the lid. Rested his hand on top of the mahogany for a moment, the way you rest your hand on a friend's shoulder before saying goodbye.
Then he took his hand away.
Some companions retired without a ceremony. He had carried the Diadem for over twenty years, and it had carried him just as long, and nobody else in the world knew what it had meant.
That was enough.