The Heavenly Illusion Reincarnation Blood Spider had most likely set up an Illusion Law divine ability at the entrance to the restriction. The moment cultivators stepped inside, they believed they were heading toward some trial checkpoint—just like the Yellow Springs Road and Bridge of Helplessness Zhang Tie had encountered earlier.
Using those illusions, it was able to lure cultivators here, turn them into blood cocoons, and leave them for later absorption of their blood vitality.
Time passed. Another three days went by, yet no new blood cocoons appeared. Only then did Zhang Tie undo the seal.
"Keep watching the Heavenly Illusion Reincarnation Blood Spider."
"Yes, Senior!" Xuan Gu replied.
Zhang Tie returned to his original spot. Several blood cocoons lay on the ground, and he moved them aside before sitting cross-legged. Taking out his materials, he continued refining what he needed to set up the formation.
Every hand seal Zhang Tie formed and every thread of immortal power he poured in was precise as though measured by a ruler. Smelting, shaping, engraving... over and over again. Xuan Gu stood guard nearby, occasionally glancing at the lake's surface. It remained calm, as if nothing strange had ever existed beneath that unfathomable sea of blood.
There was no sun or moon in the cave. Only the passage of time left invisible marks upon the stone walls. One year, two years, three years... The materials in Zhang Tie's hands dwindled one by one, while completed stone pillars and altars gradually accumulated around him. He rarely spoke, and Xuan Gu did not dare ask questions. He merely followed orders and watched the lake, occasionally helping move heavy stone materials.
By the fourth year, all three hundred and sixty-five black stone pillars had been erected.
An altar over thirty feet high stood before every three