Hajime Transmutes Sealstone

Hajime squatted down and reached for the mound of crumbled sealstone that had once been Yue’s prison.
...
Vivid crimson sparks skittered across the floor.
Hajime had used his transmutation on the pile of sealstone.
Back then, destroying the prison had taken every ounce of strength he possessed, but now the sealstone’s mana resistant properties didn’t seem to affect him at all.
...
“Before, I had a hard time transmuting sealstone. Because it dampens magic, I couldn’t even keep much of it in my Treasure Trove. Though, I guess I wouldn’t have kept it even if I could’ve, since it seemed to bring back bad memories for Yue. Anyway, the point is, I can easily mold it however I want now.”
-Volume 11
He’d combined it with sealstone, which repelled magic, and azantium ore, the hardest metal in existence, to create a unique alloy.
And he’d christened this alloy “repellite.”
Not only was it extremely sturdy, but it also deflected magic and mana
...
After his near brush with death at the Demon Lord’s castle where he’d unlocked the Transcendence skill, Hajime had grown strong enough to transmute even sealstone with ease.
...
The whole thing was also coated in sealstone to make it impossible to destroy with disintegration magic.
-Volume 12
Damn... This guy’s good... Hajime thought to himself.
Red sparks ran down his arms as he desperately tried to keep up with Oscar.
It was taking everything he had to keep the obelisk from falling apart.
Even though he was the greatest Synergist alive in the present, he was having a tough time figuring out how to repair the seal.
In fact, when he’d seen how complicated and precise the layers of magic circles that composed the seal were, he’d almost wanted to give up.
To make matters worse, the obelisk itself was created from some ore he’d never seen before, and it was a hundred times more resistant to magic than sealstone.
...
Unknown materials? Magic circles that had never been seen before? Those meant nothing to Oscar.
So long as he could analyze the structure of the obelisk, he’d be able to repair it completely.
That was just how godlike his skills were.
Hajime couldn’t help but grit his teeth in frustration when he saw how big a gap there was between their abilities
...
The two of them stared at the obelisk with absolute focus. They were like doctors performing a never-before-attempted life-saving surgery.
It took perfect coordination and every ounce of skill they possessed to repair the obelisk with the pinpoint precision needed for such a complex artifact.
The light coming off the two Synergists grew brighter.
Golden and crimson sparks ran down their arms as they used up every last ounce of mana they had.
...
“Transmute!” Oscar and Hajime cast the final transmutation needed to fix the tower completely.
Veins of golden and crimson light shot down the tower, and with a deep rumbling, the entire thing righted itself, the deep cracks disappearing like they’d never existed.
-Arifureta Short Stories