The speed of advancement and combat power of this "Black Evil Technique" entirely depends on the number of souls refined. With enough cultivator's divine souls or fierce ghosts, one can advance swiftly and continuously.
Initially, its power might not be high, but the stronger it becomes as it progresses.
However, if no souls are refined, this Black Evil Technique is merely a foundational transitional cultivation technique for ordinary outer disciples of the Soul Catching Sect.
It is essentially a technique that requires heaps of cultivation resources, but when thinking about the level of Nine Netherworld Soul Slaughter Fiend, it requires a vast amount of cultivator's divine souls or resentful spirits and evil ghosts, otherwise an immense amount of ordinary mortal soul resources.
For a Qi Cultivation Stage cultivator, it's almost impossible to succeed.
Moreover, such restrictions have led to few people choosing to cultivate the Black Evil Technique, with most only using it in the transitional stage before switching to other techniques.
So when Zheng Yi chose the Black Evil Technique in Blood Mist Abyss City, it was seen as nothing special, without any highlights.
The Elder even thought Zheng Yi chose the Black Evil Technique just to build a good foundation, intending to switch to other techniques later.
However, little did the Elder know, these issues didn't exist for Zheng Yi.
His goal this time was to cultivate to the level of Cyan Profound Fiend.
Nobody knows what happened in this playground before; the intense resentful energy formed a Land of Yin and Evil, where ghosts resurrected en masse, a forbidden place for the living.
For Zheng Yi, however, it was an excellent place to refine fierce ghosts and resentful souls.
Moreover, Zheng Yi had previously slaughtered, refining numerous fierce ghosts and resentful souls with the Soul-Catching Banner, practically sweeping the area clean.
The remaining fierce ghosts and resentful spirits were not numerous, nor too strong, just right for him to practice with.
As night fell again, Zheng Yi set up the Soul-Attracting Array once more, and hoisted the Soul-Catching Banner.
The thick bronze pole was planted into the ground, and amidst the gusting yin wind, a huge black banner unfurled, gathering thick evil qi, enveloping an area of several dozen meters around.
Zheng Yi used a spell to control the Soul-Catching Banner, releasing twenty fierce ghosts from the black mist.
Led by the red-clothed female ghost, they hid in the thick black mist.
"With the protection of the Soul-Catching Banner, cultivating this Black Evil Technique poses no danger,"
Zheng Yi was extremely cautious, maintaining such a demeanor even here, a habit slowly cultivated over years of struggling at the bottom of the cultivation realm. In fact, most loose cultivators at the bottom are like this.
The reckless loose cultivators do exist, but very few survive past the Middle Stage of Qi Cultivation.
To ensure uninterrupted cultivation, Zheng Yi cautiously released the fierce ghosts from the Soul-Catching Banner to protect himself — it was time for the magical artifact to play its part.
The Soul-Attracting Array apparently held irresistible allure for the fierce ghosts and resentful souls. Even though many had been refined here before, a decent number of fierce ghosts and resentful souls still roared their way into the black mist.
Once they charged into the black mist, the Soul-Catching Banner lit up entirely, flashing a layer of hazy black light, the churning evil qi expanded crazily, turning these fierce ghosts and resentful spirits into the blind and deaf.
Meanwhile, the hidden fierce ghosts in the black mist suddenly appeared, elusive, as they, under the lead of the red-clothed fierce ghost, tore apart the spirit bodies of the resentful ghosts one by one.
Perceiving the situation within, Zheng Yi directly used a spell to control the Soul-Catching Banner, opening a passage within.
A spirit body torn apart four or five times, the severely damaged resentful soul, was sent to Zheng Yi.
Zheng Yi didn't stand on ceremony or waste words, speed was vital, and he pressed one hand fiercely on the top of the resentful spirit following the method of the "Black Evil Technique."
The violent black evil qi surged like a thrashing octopus.
The horrifying black evil qi with spirit-corrosive properties spread, directly enveloping the entire resentful spirit inside, maniacally devouring the power of the resentful spirit.
Within about three minutes, that resentful spirit was completely absorbed.
This all coordinated perfectly; under Zheng Yi's control, the Soul-Catching Banner channeled a continuous stream of fierce ghosts and resentful spirits to his front, all becoming resources for the cultivation of the "Black Evil Technique."
Zheng Yi's cultivation speed grew faster, his technique more refined, until in the end, he could absorb a fierce ghost or resentful spirit clean in just a dozen minutes.
At the same time, the black evil qi surging on him transformed into profound yin fiend, its color resembling black oil, emitting a dark sheen.
The texture shifted from an initial gaseous state to a slightly viscous liquid, gradually changing towards a peculiar cyan-black, although the change was not very noticeable.
If one approached Zheng Yi at this moment, they could clearly feel the temperature around him seeming to gradually drop.
In the region enveloped by the cyan-black mist, bits of white frost began to form, layer upon layer, condensing without melting.
This was a sign of the technique advancing, evolving from the initial black evil qi to the subsequent profound yin fiend, now transitioning to the higher level of Cyan Profound Fiend.
Such efficiency, feared unprecedented and unparalleled among Soul Catching Sect disciples who have trained in the "Black Evil Technique."
Even if some outer disciples, possibly due to luck or family backgrounds, found a Profound Yin Gathering Evil Land, they would need to slowly absorb and cultivate, definitely not upgrading black evil qi continuously and swiftly in this manner.
Historically, there have been those who, due to cultivating the "Black Evil Technique," turned into murderous demons, or even mutated into monstrous beings.
But here, Zheng Yi could kill these fierce ghosts and resentful spirits without any scruples, feeling no guilt or remorse, seeing it as a good deed for the world instead.
He felt like he was slightly improving the 'harsh' environment for those struggling to survive in this world.
Though cultivators practice to become immortals, they're actually just humans from the mountains, and killing monsters isn't the same as killing people, it won't damage their dao heart.
The killing rampage continued throughout the entire night, and Zheng Yi finally stopped.
"Absorbing too frantically in the first half of the month, only about fifty percent refined,"
Zheng Yi opened his eyes somewhat dissatisfied, casually storing the Soul-Catching Banner, the released fierce ghosts, and red-clothed female ghost all re-entered the banner, his expression showing a bit of helplessness.
To craft the Soul-Catching Banner, he directly killed most of the fierce ghosts and resentful souls in this Ghost School.
Over one night, the "Black Evil Technique's" black evil qi transformed into profound yin fiend, but only fifty percent of it converted to Cyan Profound Fiend, indicating it was time to leave this place.
Subsequently, Zheng Yi packed up the materials for the Soul-Attracting Array and walked out of the school gates. As he turned again to look at the dilapidated school,
a ray of sunlight happened to shine down, the golden light covering the ruins, bringing a warm feeling.
Looking again, Zheng Yi faintly felt the place becoming 'cleaner.'