The earthstone heart was different from the dark heart. It was a piece of brownish stone. Those without a good pair of eyes would assume that it was a regular piece of stone that was somewhat shiny, whereas those with a good pair of eyes would be able to judge that it was an earthstone heart from its markings and the energy it exuded.

An earthstone heart was essentially a stone formed amid ancient soil, mountain, or stone through absorbing the essence of the earth. This particular earthstone heart was much larger than the one Xiang Shaoyun had previously snatched from the cannibals for Liang Zhuangmin.

A thick earth power was contained within it, and it was much harder to refine compared to the dark heart. Thus, it would take longer. However, Xiang Shaoyun understood how much the three little birds longed for the power within the earthstone heart. Thus, while he was refining the stone, he also channeled some of the stone's power over to the three birds.

That action allowed the three birds to greatly transform their bodies, building them solid foundations. Through absorbing the power of the earthstone heart, apart from a growth in strength, Xiang Shaoyun also comprehended the power of earth, which was his greatest gain.

He comprehended the thickness, toughness, and tolerance of earth, which in turn further improved his mental state again and again. The past events that had caused him joy, love, hatred, worry, and other emotions were replayed in his mind with greater clarity.

He gained a deeper understanding of karma, and his wisdom seemed to have increased as well. Perhaps that was the essence of earth, to have a heart as wide as the earth, and through having such a heart, one would be able to undertake greater responsibilities and pressure.

Unknowingly, one month passed.

During this period, flying beasts would occasionally attack, but the nether prison devil puppet killed them all. Xiang Shaoyun had gotten a month of rest, during which he had refined the earthstone heart. After refining the earthstone heart, his cultivation level had similarly only increased by a tiny bit, reaching late eighth-stage Skysoar Realm.

That was a result of him compressing and splitting off the power he gained from the earthstone heart. Nurtured by the power of the earthstone heart, the three little birds had evidently grown much larger. His astral cosmos sea had also expanded greatly, and it now also contained a certain thick and heavy aura.

Apart from that, Xiang Shaoyun's flesh had also become much tougher as well. That was the great transformation the power of earth had brought him. At present, he was seated in the nest, madly absorbing the natural earth energy from his surroundings, constantly growing in strength. The speed in which he was growing was rather astonishing.

Xiang Shaoyun wasn't content with his present situation. Although he did not continue refining the other unique items he had, he did not idle around. He started focusing on his battle techniques instead. This time, his battle technique cultivation was done with an emphasis on the powers of earth and darkness.

Without corresponding battle techniques to use alongside his two newly gained powers, it would be a waste. Unfortunately, he had only started cultivating his battle techniques for a few days when he was finally attacked by evil spirits.

The so-called evil spirits were actually remnant soul bodies. They were once extremely powerful and evil existences, and although they were no longer as strong as they once were, they could still easily take on regular Emperors.

The evil spirits currently before Xiang Shaoyun were roaming around mindlessly. Drifting together with the wind, they arrived near the nest. When they arrived, they seemed to have transformed into demons, and immediately bared their fangs at Xiang Shaoyun.

These low-level evil spirits were capable of dealing large damage to one's soul. The moment one's soul was corroded, one would be assaulted by madness, eventually losing one's mind completely. This was the scariest aspect of the Back Graveyard.

The reason why Xiang Shaoyun hadn't met these evil spirits before this was due to the location he was hiding at. Apart from that, he had also been lucky. Now, with wind blowing in the nest's direction, the evil spirits were brought over as well. They appeared like a violent tide, one that Xiang Shaoyun couldn't escape even if he wanted to.

Initially, he wrapped Yun Flame's power around himself and the three little birds. It discouraged the evil spirits from approaching, and some who dared approach were immediately ignited and killed. But there were too many evil spirits, enough to flood the entire mountain they were on. If he couldn't set the entire mountain aflame, he wouldn't be able to avoid their endless tide.

To make matters worse, Xiang Shaoyun could sense that there were even more terrifying evil spirits in the depths of the Back Graveyard. Perhaps those powerful evil spirits would suddenly come out as well. At that time, he wouldn't be able to hold on anymore.

"No, I can't allow this to continue. I need to think of something," muttered Xiang Shaoyun as he sank into thought.

He was contemplating releasing all the ghostrunes. The ghostrunes would have no trouble dealing with these evil spirits. However, he ultimately decided against it. The ghostrunes were one of his trump cards. Unless absolutely necessary, he wasn't willing to show them.

"Since I can't release them, I should just let these evil spirits in instead," decided Xiang Shaoyun as he withdrew Yun Flame's power.

The instant Yun Flame's coating vanished from his body, his head was swarmed by an endless torrent of evil spirits. Even an Emperor would not be able to survive something like this. However, he remained seated with complete calmness. His eyes shut, he allowed the evil spirits to invade his mind, acting like he was completely ignoring them.

In truth, within his head, the Nether Soul Domain had formed an independent world. The moment the evil spirits entered, they landed in the independent space. Once inside, regardless of what they did, they weren't able to deal any damage to the space.

When the 8,000 ghostrunes saw the evil spirits, their eyes lit up with excitement as they quickly swarmed and devoured the evil spirits. The evil spirits might be vicious, but the ghostrunes were their nemesis. The evil spirits weren't even able to deal the ghostrunes any damage before they all turned into food.

Even after devouring so many evil spirits, the ghostrunes still looked hungry. When Xiang Shaoyun sensed that, his lips curved into a smile as he completely removed his defenses, allowing the evil spirits to enter his mind as they wished.

Unsurprisingly, all the evil spirits turned into ghostrune feed, allowing the 8,000 ghostrunes to undergo a massive growth in strength. One could say that the evil spirits were akin to a tonic that was even more useful than soul medicines to the ghostrunes.

The ghostrune patriarch grew into a seventh-stage Emperor, and over a dozen new Emperors had appeared among the ghostrunes as well. In total, there were now more than 50 Emperors among them. As for the Kings, their cultivation levels had also advanced greatly.

This rapid advancement was an accumulation of growth from the time Xiang Shaoyun left the Devil Domain until now. Along with the increase of his strength and the awakening of his devil blood, the Nether Soul Domain had also changed, greatly benefiting the ghostrunes. In fact, just the ghostrunes alone were comparable to a tier-5 organization. And when the unique attacks of the ghostrunes were taken into consideration, they could easily destroy regular tier-5 organizations.