The Tree Demon smiled, then extended a branch with a emerald green leaf on it.

Ling Feng frowned slightly, unsure why the Tree Demon elder would give him a green leaf.

"This is a Leaf of Nature!" the Tree Demon slowly said, "It can sense whether you possess any evil qi. If you do, it will immediately wither; if not, it will remain fresh and green!"

Ling Feng took a deep breath, gathering all his aura. Once he felt he had concealed all his evil qi, he reached out to take the Leaf of Nature.

But when the Leaf of Nature fell into his hands, it withered rapidly at a visible speed, turning into a dried leaf in the blink of an eye!

"How is this possible!" Ling Feng looked at the dried leaf in disbelief, murmuring to himself, "I have concealed all my aura, how could this happen!"

"Though you think you’ve concealed your aura enough to deceive others, you cannot deceive nature!" the Tree Demon said calmly, "Your ability to conceal your aura is still lacking!"

Ling Feng’s expression was uncertain; he felt his confidence had been greatly shaken.

The Tree Demon spoke softly, "Young one, I understand your thoughts, but I can tell you that I didn’t tamper with anything. This Leaf of Nature contains the purest Force of Nature in the world!"

"Entering the Element Tower is simple. Comprehend the Force of Nature within the Leaf of Nature and revive its vitality, then you can enter here!" the Tree Demon said calmly, "Otherwise, I won’t let you in."

Ling Feng took a deep breath and said to the Tree Demon, "Alright, elder, I will definitely comprehend the Force of Nature within the Leaf of Nature!"

The Tree Demon nodded and said, "You can stay here. When the Leaf of Nature in your hands revitalizes, it means you’ve reached the standard to enter!"

After speaking, the Tree Demon’s vines returned to the earth, while Ling Feng sat with the withered Leaf of Nature, falling into contemplation.

Ling Feng didn’t understand why the Leaf of Nature withered despite his efforts to conceal his aura. Was it really because his ability to conceal aura was insufficient?

This thought faded, as Ling Feng immediately rejected it. He still had confidence in his abilities; even a Half-step Immortal might not detect him.

If cultivation technique and strength are not the reason, then what is?

Ling Feng fell into deep thought, and after a long time, he immersed himself in the withered Leaf of Nature. Upon careful inspection, he found no differences.

Days passed, and Ling Feng still made no progress. Feeling restless, he stood up and walked towards the depths of the forest, thinking he needed to change his approach, certain he had overlooked something.

Ling Feng concealed his aura, wandering for about an hour, noticing no wildlife approached him along the way.

"Something’s not right!" Ling Feng frowned; having concealed his aura, why wouldn’t the wildlife approach? Had they sensed his presence?

Ling Feng took a deep breath, sensing a strong aura not far ahead, and rushed towards it.

The aura’s owner seemed panicked, but Ling Feng’s speed was quick; he reached it before it could flee.

"It’s actually a Leopard!" Ling Feng said sternly, "Did you already sense my presence before I came?"

Facing the formidable Ling Feng, the Leopard trembled, crouching in place.

"Don’t be afraid, as long as you truthfully answer my questions, I won’t harm you!" Ling Feng said.

The Leopard raised its head, cautiously observing Ling Feng. Seeing Ling Feng’s calm face, it hesitantly said, "Master, indeed I sensed your presence before!"

"How is that possible, I’ve concealed my aura!" Ling Feng asked puzzled.

The Leopard explained, "Master, we creatures living in the Carefree Forest have a sharp sense of external dangers. Though you’ve perfectly concealed your aura, when you approached, I felt a sudden tremor in my heart."

"A tremor in your heart?" Ling Feng frowned, "What do you mean?"

The Leopard whispered, "I felt your presence because I sensed the pressure from the depths of your soul."

"From the depths of my soul?" Ling Feng seemed to understand; it’s not his aura concealment that’s inadequate, but the pressure and evil qi within his soul?

But how to eliminate the evil qi from the soul? Ling Feng sighed, feeling troubled.

Having experienced countless battles, the pressure and evil qi from Ling Feng’s soul had formed little by little through battle, making elimination challenging. Plus, he had no method to remove such soul evil qi.

"Master, I’ve told you all I know!" the Leopard trembled as it spoke.

Ling Feng waved his hand, and the Leopard, as if pardoned, dashed away.

Returning to the Tree Demon, Ling Feng sat again, realizing through the Leopard’s words what might be happening.

He looked at the withered leaf in his hand, muttering, "Leaf of Nature, do you wither because you sensed the evil intent in my soul? So, only by controlling the evil intent in my soul can you regain vitality?"

Ling Feng sighed, gradually calming down, slowly closing his eyes.

Though Ling Feng lacks clues presently, he knows to solve this problem, he must penetrate the secrets within the Leaf of Nature!

"The Tree Demon elder mentioned this Leaf of Nature contains the Force of Nature; I believe the Force of Nature is key to solving this problem!" Ling Feng thought to himself.

But how to comprehend this Force of Nature? Ling Feng felt stumped; he had examined the dried leaf dozens of times but found no trace of the Force of Nature.

"Where exactly is this Force of Nature?" Ling Feng sighed, then looked at the giant bird atop the Tree Demon.

The giant bird perched quietly on the huge tree, seemingly resting. Ling Feng didn’t know when it would leave, so he had to unravel the secrets of the Leaf of Nature before it did. Otherwise, if the giant bird left, where could he find it?