Ju You Ghost Flame, such a rare treasure in the Underworld would surely provoke countless Demon Kings to vie for it if its existence were revealed. Moreover, Ju You territory is where all major factions converge most densely. If Demon King Tian dares to march his entire army into this region openly, he wouldn't remain undiscovered for more than two days before attracting endless troubles.

Therefore their procession traveled light. They only boarded one warship - the personal flagship of Demon King Tian, no longer than dozens of meters yet painstakingly forged with countless spirit stones. This vessel excelled in speed, stealth and combat capabilities alike.

The crew was also minimal. From Demon King Tian's side it consisted merely of himself, Tulei and ten elite demon generals. As for the Thunder faction, four members had assembled - including Qifei whom Thunder originally wanted to leave behind in Tian Gui City to recover from her injuries. But she refused to part company with them at all costs, so they reluctantly brought her along despite her spirit wounds only healing about seventy percent. Fortunately her cultivation remained intact so self-preservation wasn't an issue. After entering the abyss she'd just stay aboard the warship.

To ensure Qifei's safety, Thunder gave her forty Yin Heaven Thunder orbs - with these protective talismans even if she encountered a yuan level cultivator alone, they could force a retreat.

During their journey Thunder began studying Ju You cultivation techniques under Demon King Tian's guidance. The elder once again demonstrated his characteristic generosity toward juniors, never withholding any knowledge from Thunder's questions. Within mere months Thunder's understanding of Ju You arts had ascended to unprecedented heights, and he learned many hidden truths about demonkind.

For instance, some refined spirit demons could begin learning basic Ju You techniques when reaching general rank after gradual evolution and intelligence growth over time. But why did human-controlled high-grade demons mostly rely on instinctive talents? The blood sacrifice technique humans used to command demons erased their free will through deep spiritual bonds, reducing them into obedient automatons.

Human-created demon servants evolved either by the master's blood refinement or by devouring souls and flesh for rapid growth. With strong enough masters they could mature refined demons in mere years. But a naturally evolved general-level spirit demon needed centuries to slowly develop intelligence through experiences and survival struggles - their innate wisdom far surpassing those artificially matured counterparts.

Even if humans spent years cultivating high-grade demons, the creatures would mostly remain confined in soul-nourishing towers without any external communication or learning opportunities. No matter how intelligent a race might be, being raised this way could never produce truly wise beings. Knowledge and experience were separate from innate intelligence entirely.

This explained why even naturally intelligent high-grade human-bred demons couldn't learn Ju You techniques - unless they belonged to the rare Tianling Ghosts whose bloodline inherited the ability to perceive cosmic laws directly. Demon King Tian himself admitted he knew little about these celestial gifts, as even in Underworld only one appeared every millennium.

Now Thunder finally understood why his long-time companion demon remained silent and speechless despite years together - until Xiao You's guidance triggered a massive intelligence leap allowing basic communication. He had always treated demons as weapons rather than living beings, never interacting with or educating them. Even now the refined demon Achu's intellect paled against naturally evolved generals.

Without Xiao You and Demon King Tian's revelations, Thunder would've kept his demons locked away in soul towers like most blood-sacrifice cultivators - explaining why Xiao You despised those towers so much. Of course Demon King Tian warned about risks: cultivating independent-minded sentient demons might lead to rebellion just as he himself would never accept slavery.

After careful consideration, Thunder decided to treat demons as conscious companions rather than tools. From Xiao You's example he saw loyalty remained strong despite independence - the blood bond created deep familial connections through shared life essences. With sincerity and respect, regular communication and education, even blank-slate demons could become loyal friends without betrayal risks.

This philosophy shift led Thunder to constantly keep his elite demon Achu and soul-eating phantom tiger Xiao Ying outside their containment chambers for interaction and teaching. Within months the gifted Achu became increasingly human-like with active personality development, while Xiao Ying formed strong bonds with Thunder under his guidance.

He shared these insights with Oriental Fu and Wan Yan who immediately adopted similar methods to cultivate their elite demons - in fact female demon cultivators had already surpassed him in bonding with their companions. As for Qifei whose two refined demons perished, Thunder secretly gave her replacements. With his new cultivation philosophy he'd never lack elite spirits again; Qifei followed suit by keeping her new demons at low general ranks to focus on nurturing their intelligence during recovery periods.

Of course this required consistent effort over time - but it was never too late to start now.

On this particular day they finally reached the Ninth Layer of Underworld, the Ju You territory. Even Demon King Tian grew exceptionally cautious here, extending his vast spiritual perception up to three hundred miles radius - an impossible feat for a mid-rank demon king normally. He achieved this through "Truth Revealed", a special item Thunder had acquired from Qian Luo.

Though important to himself, Thunder felt he must repay Demon King Tian's many favors and knew more copies would return with Zhaozhou's blood demons soon. So he made the generous gift which impressed even the elder demon king - allowing mid-tier perception abilities to reach peak demon king detection distances. Of course this only expanded range without actually enhancing spiritual power itself.

With this protection their safety significantly improved. Unless facing peak yuan or transcendent huashen level masters, Demon King Tian would always detect threats first. After all encountering a random peak yuan here was astronomically rare - even ordinary yuan weren't common as street vegetables let alone transcendent level beings. Only four such huashen exist in Underworld, all high-ranking recluses with no reason to wander alone.

They smoothly arrived at Ju You Abyss's outer perimeter after incidentally slaying two yuan monsters en route for minor gains.

Standing on the warship deck, Thunder gaped at the endless abyss of darkness stretching infinitely. Crimson lightning crackled through towering vortexes that choked the air. A lone danjing level beast fled desperately toward the edge when suddenly a massive four-meter snake head emerged from below - it coiled up to swallow the creature whole before retreating back into depths. The obsidian serpent's three-exposed segments already reached forty meters in length.

As it vanished, Thunder could feel its cold gaze sweeping past their vessel with disdainful challenge in those lifeless eyes.