One week later.

Nidhogg’s body was gaunt, weak, and frail. Even just sitting in front of the lab bench reading, beads of sweat appeared on his pale face, his eyes bloodshot, and his breathing was labored and weak.

Peran Ornos looked at this indifferently and said, "It seems oral ingestion is indeed more effective than respiratory infection. When I was guided by my mentor to infect myself with lymph, it took me three weeks to show symptoms like yours." As he spoke, Peran Ornos shook a vial of green potion, observing the life aura emanating from it, and handed it to Nidhogg.

Nidhogg took the potion and drank it down in one gulp. Immediately, he felt a surge of life energy nourishing his body, slightly alleviating his weakness.

Taking out his crystal ball, Nidhogg lightly probed it and then gave a bitter smile. His physical strength had already dropped to 2?

Peran Ornos shook his head, putting the empty vial away. While using his mental power to scan the large array of text in his crystal ball, he nonchalantly said, "In the natural world, if creatures were infected with lymph and lacked treatment options, those few months of weakness would be a death sentence. But in a wizard's lab, you just need to quietly wait it out. There's nothing here that will threaten your life. Consider it a serious illness."

"Okay," Nidhogg mumbled in response, closing his book and, extremely fatigued, fell asleep on the corner bed of the lab. Peran Ornos glanced at Nidhogg, seemingly reminded of himself in his youth, sighed, and quietly left the lab.

...

Two months later.

Nidhogg lay in bed, nearly in a state of death, his body emaciated to skin and bones, eyes dim and unfocused. He wanted to get up to continue the experiment he left unfinished, but found himself utterly without strength.

Peran Ornos frowned, "It only took two months to reach the rapid proliferation stage; is this due to the oral lymph? If so, that's a month faster than expected." After speaking, Peran Ornos parted Nidhogg’s eyelids with his withered fingers. After performing a simple light sorcery, he confirmed that Nidhogg's pupils still had a slow reaction.

"Is the short time causing the life energy absorbed by the body to be insufficient to meet the energy demand of the extensive lymph proliferation?" After pacing the room a few times, Peran Ornos suddenly called softly towards the room's entrance, "Gahae."

A sleek black cat came running with its black tail raised, "Old man, what is it?"

"Leave a bit of your scent on him," Peran Ornos pointed at Nidhogg, who looked like he was close to death.

"Leave a bit of scent?" The black cat glanced at Nidhogg’s sorry state, softly murmured, "Geez, being reckless enough to drink that thing, now I have to save you." Saying this, the black cat jumped onto Nidhogg, raised its hind leg, and left a stream of liquid on his face.

After urinating, the cat jumped back to the ground and said, "Done."

"Hmm," Peran Ornos acknowledged, then picked up the gem pearl from the lab table and placed it into Nidhogg's mouth. This gem, a tool Nidhogg had acquired from a fat man, allowed underwater breathing when held in the mouth. Although Nidhogg hadn’t had a chance to use it before, Peran Ornos now put it to use.

With a light pat from Peran Ornos, a wave of magic coursed over Nidhogg, and his body began to float as if gravity had lost its effect, creating some form of repulsive force with the ground.

Shortly after, with a splash, Nidhogg was tossed into a large tank where the sawfish were kept.

Perhaps due to the cat urine, the fierce-looking sawfish fled frantically to the far side of the tank as soon as Nidhogg entered the water.

...

Three days later.

When Nidhogg slowly opened his eyes, he found himself lying underwater and instinctively began to struggle. His body's extreme weakness made his struggle appear feeble.

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Tap, tap, tap.

Nidhogg heard a sound and forced himself to calm down. Turning his head, he saw the black cat tapping on the tank. The cat mouthed, "Rest for another day; your master and mistress are preparing restorative food for you." Despite the muffled underwater sound, Nidhogg managed to understand, blinking twice to signal that he heard.

Lying in the water, Nidhogg was both puzzled by his ability to breathe underwater and surprised by the sawfish that dared not come near. He started to sense his body's condition, noticing the tank and the water it contained had some peculiar function, generating a nurturing rare energy. Although still weak, Nidhogg felt the lymph inside him had reached a symbiotic phase, having maxed out his body’s capacity and ceased proliferating.

Feeling exhausted, Nidhogg closed his eyes once again.

...

Two months later, with crystal ball monitoring, Nidhogg's body had fully recovered, his physique reaching 6 points. Initially, it should have been 7, but 1 point was lost permanently due to excessive cellular energy consumption in a short period.

Worth noting, the first thing Nidhogg did after regaining autonomy was to concoct a bottle of odor-eliminating potion to remove the scent left by Gahae (the black cat), maintaining a completely odorless condition (activating a low-profile aura).

Peran Ornos nodded approvingly, "Recovering well. Now you can officially begin the Mixed Venom Body Refinement training. However, given your low physique, you'll only use non-lethal irritant toxins. Typically, wizard apprentices practicing Mixed Venom Body Refinement would ingest or inject mild toxins under a mentor’s guidance, but here, we have a better option."

Saying this, Peran Ornos led Nidhogg into a room sealed with magical restrictions, retrieving a fully enclosed metal container from within.

"Inside is a piece of precious low-intensity Radiant Stone. Even though it’s low intensity, if exposed in the civilian world, people within fifty meters would weaken and die within a day, and those within a thousand meters would experience varying degrees of poisoning. It needs strict monitoring as a hazardous item." Peran Ornos explained, "But for your preliminary auxiliary training, it’s perfect. First, it won't have irreversible fatality; second, it’s reusable, only requiring you to manage your exposure time."

A moment of delight passed over Nidhogg as he accepted the container, asking, "How much physique can I gain from training with the Radiant Stone each time?"

"Around one point," Peran Ornos confirmed. "After each training session, your body will recover over a month, allowing you to reach a physique of over 15 within a year using the Radiant Stone. Eventually, your physique will improve, and lymph barriers will evolve resistance to the stone’s toxicity, diminishing its effectiveness. Then I’ll guide you in true toxin formulation."

Passive evolution?

Nidhogg noted the keyword used by Peran Ornos.

Due to its incredible adaptability, lymph boasts strong passive evolutionary capabilities. Wizards leverage this trait to develop the Mixed Venom Body Refinement Sorcery, allowing lymph to form a thick ‘armor’ across all cell surfaces, enhancing cellular ‘physique.’

While the human body naturally possesses passive evolutionary abilities—most life forms do—its adaptability and evolutionary speed are substantially inferior to the simple lymph structure, incomparable even. Thus, wizards never considered leveraging the body’s innate passive evolution.

However...

Nidhogg was different.

Thanks to the symbiotic parasite Salmacis, Nidhogg’s passive evolution significantly surpassed that of normal humans. This implies his cells benefit from dual evolution inside and out.

In other words, Nidhogg’s monthly Mixed Venom Body Refinement would have twice the effectiveness!

These thoughts were mere conjectures, not yet confirmed.

Peran Ornos took Nidhogg to a spacious, sealed chamber. "Radiant Stone must be used in such a restriction-sealed room; otherwise, it will transmit through some bandwidth into the surrounding space. The old guy downstairs is tolerant, but if those above are around and in a bad mood, it would be troublesome."

Nidhogg nodded, indicating he understood.

"Hmm," Peran Ornos said, opening the restrictions. He carefully uncovered the metal container, revealing an ordinary-looking black stone to Nidhogg. Instantly, Nidhogg’s body reacted with an unexplainable repulsion, cells sensing a threat instinctively.

"The first time, half a minute will suffice," Peran Ornos said, closing the metal lid after thirty seconds, carefully storing it back in the secure room.

Nidhogg felt dazed and slightly weak, asking, "Mentor, how long will my weakness last after training at this stage?"

Peran Ornos pondered, "Currently, you’re exposed to mild toxins, so the weakness should last a day. During this time, lymph passively evolves, absorbing much of your body’s energy, reducing your usual physique by half. Avoid Mixed Venom Body Refinement while exploring the wilderness. After about ten days, your physique will begin to increase, thanks to strengthened lymph barriers on your cells. The following twenty days allow lymph to self-regulate and rest, preparing for the next passive evolution."

...

Ten days later, holding the crystal ball, Nidhogg murmured in delight, "Physique 8, indeed a 2-point increase! As expected, the dual passive evolution from Salmacis and lymph grants my cells dual refinement!"

Excitedly, Nidhogg considered the benefits he would receive.

Firstly, accelerated training, needing no further explanation. Secondly, higher physiological resistance to weaker toxins suggests a more significant buffer, allowing Nidhogg to forego precisely matching the toxin extremities required by Peran Ornos.

With this, Nidhogg could save substantial time for further sorcery knowledge exploration.