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Linus was a natural...
He went ham on the Nightmare Crystal Worm, harvesting all the crystal ores that grew on the surface of its body with his pickaxe. He was in tune with his instincts, reducing the effort he needed to remove the ores.
After three hours of non-stop mining, a small crystal ore mountain piled up underneath the suspended crystal worm. Linus was still up there, hacking away at the remaining ores.
Despite his obvious signs of weakness due to exhaustion, his eyes remained bright and determined; it's as if he couldn't sense the state of his body at all.
He tripped once or twice because he was really tired, but instead of taking a moment to rest, he instead gobbled up raw crystal ores, which gave him an immediate boost of strength and energy to keep going; that's how he's able to last for so long.