Following Zhagu deeper into the fortress, they descended continuously — a full thousand zhang underground — before suddenly emerging into an enormous cavern.
A wall of heat struck them in the face.
Yang Kai looked around, and a flicker of surprise crossed his features, because flowing naturally through this subterranean cavern was earth fire, and the omnipresent waves of heat radiating throughout the space were its doing.
Traces of human restrictions adorned the interior. The entire cavern was enveloped by a grand formation, and the nexus where the earth fire converged sat precisely at its center.
Scattered around the cavern's perimeter were all manner of materials, many of which appeared to have been previously used.
Yang Kai frowned, puzzled by what he saw.
Zhagu strode directly toward the formation's center. The aura of a living being seemed to activate the formation's power, and tongues of earth fire — hot enough to melt metal and devour jade — licked hungrily at Zhagu. He paid them no mind, channeling Ink Force to enshroud his massive hand before plunging it straight into the fire.
When he withdrew his hand, it clutched an object.
Zhagu retreated from the formation's center and tossed the item to Yang Kai. "Take a look at this."
Yang Kai reached out to catch it, and his arms dipped slightly under the weight. For someone of his brute strength to react that way spoke volumes about how heavy the object was.
It was a great halberd, roughly five zhang in length and as thick as a man's leg. Holding such a weapon looked somewhat absurd in Yang Kai's hands, but it was clearly proportioned for someone of Zhagu's stature.
"This is…" Yang Kai examined the halberd with astonishment. A quick sweep of his divine sense yielded answers. "A human-forged weapon?"
He turned to look at Zhagu, eyes wide with surprise. "Where did this come from?"
With his trained eye, he could readily see that although this halberd had been crafted by a human artifact refiner, it was far from complete — only a rough framework at best. Such a thing would be useless on the battlefield; under the power of a human Open Heaven realm cultivator, it would shatter easily.
"I had an Ink Disciple under my command. The fellow knew a thing or two about artifact refining, and he spent considerable time and resources to forge this for me."
Yang Kai blinked, taken aback. He hadn't expected that.
"The reason I set up my residence here was also his idea. There's earth fire in this cavern that he needed for his refining work, which let him do what he did best. Unfortunately, he never finished the job before he… But before he left, he made arrangements and told me to leave the halberd soaking in the earth fire. After a hundred years, it might be usable."
Yang Kai shook his head. "It won't work. The foundation is flawed — no amount of nurturing will make a difference."
Zhagu raised an eyebrow. "What do you mean?"
Yang Kai said, "I don't know what level your Ink Disciple's refining skills were, but in my opinion, the forging technique was crude beyond measure. This Artifact's foundation was set from the very start. Even if you nurture it for a hundred years, the best you'll get is a lower-grade Artifact."
Zhagu's eyes brightened slightly. "Does that mean your refining skill surpasses his?"
Yang Kai smiled with quiet pride. "Naturally."
Zhagu couldn't contain his excitement. "If you were to work on it, what kind of weapon could you produce?"
Yang Kai considered for a moment. "The Artifacts used by human Open Heaven realm cultivators are generally divided into three grades — upper, middle, and lower — corresponding to the three tiers of the Open Heaven realm. Only those who can forge upper-grade Artifacts are considered grand master–level refiners. My skills are passable at best, far from grand master level, but forging a middle-grade Artifact wouldn't be a problem."
After ten years of rigorous study in the art of artifact refining — and with Chai Hao, a disciple of the Divine Cauldron Grotto-Heaven, as his teacher — Yang Kai had made considerable progress. Chai Hao was the sixth disciple under Dongguo Anping. While his refinement skills couldn't compare to a grand master like Dongguo Anping, he was firmly a master-level refiner in his own right. Under such a person's direct tutelage, even the least talented student would improve given ten years.
Moreover, artifact refining and alchemy shared many common principles. Yang Kai himself was a Seventh-Order Open Heaven cultivator with exceptional comprehension, and in those ten years studying under Chai Hao, his skills had advanced by leaps and bounds.
His current level in the Dao of artifact refining could be considered having truly entered the discipline.
That said, talent was an immutable ceiling. Yang Kai would never achieve greatness in artifact refining — perhaps someday he might reach the point of forging upper-grade Artifacts, placing him at the grand master level. But that would be his absolute limit, a boundary he could never surpass in his lifetime. He would never rise to the heights of someone like Dongguo Anping.
Having studied under the Divine Cauldron Grotto-Heaven, Yang Kai's eye for refinement was far beyond that of an ordinary artisan, regardless of his current skill level. Every crude deficiency in this halberd was laid bare before him at a glance.
What he hadn't expected was that Zhagu had once employed an artifact refiner. Judging by the forging technique applied to the halberd, that refiner's skill was truly mediocre. And since the man was nowhere to be seen, he had likely fallen on the battlefield. Fortunately, the refiner had made arrangements before his end — leaving the halberd to slowly mature in the earth fire so that Zhagu could eventually obtain a lower-grade Open Heaven–level Artifact a century later.
But for a Domain Lord of Zhagu's cultivation, wielding a lower-grade Artifact in battle would provide precious little enhancement to his combat strength.
On the other side, Zhagu's expression grew even more excited. "You'd better not be lying to me."
Yang Kai snorted. "Why would I lie to you!"
"Words are cheap. Forge me one Artifact matching this halberd's design first. I'll supply all the materials. If you succeed, I'll reward you handsomely."