The world reassembled itself around Cassius with a low hum and a rush of cold air.
Stone walls materialized from the swirl of light, followed by the scent of frost, dust, and age.
The echo of his arrival spread through the vaulted hall like a ripple through still water.
He was home.
Nurmengard.
Once a prison, now repurposed—its cruel cells transfigured into study halls and libraries, its damp corridors lined with candlelight.
The heart of Grindelwald's domain still beat faintly beneath the stone, a fortress of silence and secrets buried deep within the Austrian mountains.
Cassius adjusted his cloak and straightened, feeling the hum of his wand stir faintly against his thigh.
He had not stood in this hall for almost a full year.
A year of correspondence through two-way glass acting like a video call, of solitary study guided by Grindelwald's cryptic lessons provided via parchment in letters
He had grown since then.
Taller, stronger, more controlled.
His magic no longer lashed wildly as it once had, having completely solidified into his core.
And yet, as the silence thickened, Cassius realized something was off.
The air was charged—too still, too heavy.
Then he saw him.
At the far end of the hall, atop the dais beneath the broken sigil of the Deathly Hallows carved into the marble wall, stood Gellert Grindelwald.
He was dressed not in his usual pale robes but in darker garb—an old duelist's coat of deep gray, its silver clasps faintly gleaming under the torchlight.
His face was as sharp as ever, though the years had carved deeper lines around his eyes.
And in his hand—his wand was drawn.
"Mentor," Cassius said quietly, inclining his head. "I have returned."
The old man's mismatched eyes regarded him coolly.
"You have," Grindelwald said, his voice calm but edged. "But you have been gone for quite some time, it is now time to see you tested, to gauge if all those years spent instructing you were not in vain."
Cassius's brows furrowed.
"what does that mean?"
A faint smile ghosted across Grindelwald's lips.
There was no warning.
A crimson jet of light streaked across the hall.
Cassius barely threw himself aside in time, the spell scorching past and detonating against a column with a sharp crack.
"Protego!"
A shimmering shield flickered before him, barely holding as another barrage came—stunners, disarming charms, binding hexes, cast in quick succession with impossible precision.
He didnt even get a moment to revel in the fact that he's managed his first shield charm something he should not learn until his forth year at hogwarts, and on his first attempt at that.
Cassius ducked, spun, and countered where he could, his wand hand moving in tight, efficient arcs.
He sent a flurry of pebbles from the floor flying upward with a swift Wingardium Leviosa, wishing he could transfigure them into knives flying towards his mentor, rather than just pelting him with pebbles.
"Too slow!" the old wizard barked, his voice echoing. "You think with your head, not your instinct!"
Cassius gritted his teeth and rolled under another curse.
Sparks lit the air.
He cast Expelliarmus, but Grindelwald countered with a flick, turning the spell into harmless light.
They circled now—teacher and student, predator and prey.
"Your wand sings, boy," Grindelwald said between spells, his tone almost admiring. "It is no ordinary one. What did Ollivander give you?"
"Something ancient," Cassius replied, deflecting a hex with a narrow twist. "Something that chose me, just as much as i chose it."
A flash of curiosity flitted across Grindelwald's gaze.
He had afterall previously held an ancient wand, the elderwand, and now he faced off against another different ancient wand.
His next curse—an intricate chain of blue fire—snapped through the air.
Fiendfyre though with his own personal touch to it, a touch that shouldnt be known to cassius, the flames were controlled so much so that, they could tell the difference between friend and foe.
Cassius's eyes narrowed.
He raised his wand wordlessly, channeled power—silent casting, one of the few techniques Grindelwald had drilled into him.
Only ever in theory since silent cast was not possible with the training wand.
Lumos.
The tip of his wand flared to life—but the light was not white.
It was green.
A deep, unsettling emerald that filled the chamber with a cold glow.
Grindelwald's eyes widened fractionally.
And before he could speak, Cassius raised his wand again and called out—clear, steady, and deliberate:
"Avada Kedavra!"
The 'Killing Curse' flashed forth like a spear of emerald fire—but it was thinner, weaker than the true thing, dissipating before it reached its mark.
Still, it was the incantation, and it was real enough to make Grindelwald falter, just for a second.
Before realizing that it was a fake.
Simply a lumos charm cast out from the wand tip, with a greenish coloration rather than the real sickly green glow of iminante death.
A second Cassius took full advantage of.
"Expulso!"
The floor erupted beneath Grindelwald's feet, shattering marble and throwing dust and debris into the air.
For a heartbeat, Cassius thought he'd done it—until the old man appeared behind him, silent as a wraith.
"Not bad," Grindelwald murmured.
Then the world went white.
A nonverbal Stupefy caught Cassius square in the back, hurling him forwards across the hall.
He hit the ground hard, rolling once before coming to a stop, wand still clutched tightly in his fingers.
He coughed, smoke and dust swirling around him, but refused to let go.
His wand burned in his grip—not in pain, but in recognition.
It wanted to keep fighting, to bring him victory.
He pushed to his knees, raised his wand again—but Grindelwald was already lowering his own.
Seeing a simple look of shock on his mentors face, a stunner like that should have rendered Cassius out of the fight, not rising to continue.
"That," the old man said, voice softened now, "was enough."
Cassius froze.
Grindelwald walked toward him, his expression no longer cold but thoughtful, even proud.
"Good trick, though careful in it's use since if you use it to often word about your feint will spread, but in a catch it will certainly create an opening espeicially if follow the fake with the real thing, making your opponent think they do not need to dodge the spell itself."
He stopped before the boy, eyes gleaming faintly in the torchlight.
"I did not expect you to win. I expected you to grow. Spellwork is only half the puzzle, battleskills are the other half, "
Cassius met his gaze evenly.
"And if I had succeeded?"
Grindelwald chuckled. "Then I would be having this conversation from the floor, while choosing to rethink my entire life."
The silence that followed was not awkward, but heavy with meaning.
Finally, the old man reached out and placed a hand on Cassius's shoulder.
"You have come far. You are ready for Hogwarts now—for the world that will not know what to make of you."
Cassius's jaw tightened slightly.
"And what of you, Metor? You seem… changed."
Grindelwald's expression flickered, just for a moment.
"Age catches even those who once outran it," he said softly. "And i must be ready to play my own part in your plans afterall."
He turned then, walking back toward the raised dais.
"Find your other partner," he said over his shoulder. "Before you return to England. you will need you hidden wand to protect yourself, while your true wand remains in the open."
Cassius rose, brushing dust from his sleeve.
His mentor was right, his return to Nurmengard was never to challenge his mentor but to set off to get his off-hand wand from Gregorovich, since as almost every aspiring dark wizard knows the ministry can review your wand and discover the spells you've recently cast, but what if you used a different wand?
Hence his public and private wands, one that would serve in the dark while the other was only used in the light.