"Before learning the Mixed Venom Body Refinement Sorcery, you need to first understand that this sorcery originates from the body refinement system of the subterranean wizards, rather than the spirit-based elemental sorcery of the Wizard Continent," said Peran Ornos as he slowly pulled out a black crystal ball from his sleeve. "This is a crystal ball used by subterranean wizards. It's capable of measuring a wizard's physical attributes. I'm giving it to you."

Nidhogg opened his mouth, then awkwardly pulled out a similar black crystal ball and said, "Mentor, I already have one..."

"Already have one... have one... have one…" Nidhogg’s voice echoed in Peran Ornos's mind. If not for his ability to control blood flow, Peran Ornos might have blushed with embarrassment.

"Ahem, you rascal. Well, since you have one, I’ll save this crystal ball." Saying so, Peran Ornos continued, "First, tell me how you categorize toxic substances."

Nidhogg thought for a moment and then replied uncertainly, "There are three main types, right? Animal-secreted toxins, plant-secreted toxins, and metallic elemental toxins?"

"Hmph, so it’s indeed categorized based on antidote types, huh?" Peran Ornos snorted with slight disappointment, then asked, "If you mix antidotes for animal-secreted and plant-secreted toxins, would they work?"

Nidhogg frowned and slowly shook his head.

Peran Ornos walked to a counter, opened a cabinet, and took out a scroll, spreading it on the test bench in front of Nidhogg. This scroll seemed to be made from some unknown leather, emitting a slight green hue due to its age, yet it showed no signs of distortion, wrinkles, or damage.

"Take a look at the classification of toxins on this scroll," Peran Ornos pointed to the ancient script on the scroll.

The ancient script was different from modern writing, and Nidhogg could only slowly translate it. After half an hour, he was surprised and said, "Classified based on the reactions of a life form after being poisoned?"

According to the scroll, poison wizards divided all accessible toxins into seven categories.

The first is hemotoxic toxins, which, when entering a life form, aim to kill, destroy, or coagulate the blood; the second is neurotoxic toxins, aiming to disrupt the nervous responses of a life form; the third is reactive toxins, which disable the detoxification process of a life form, thereby hindering its biological functions; the fourth is necrotic toxins, with strong acidity that destroys cellular structures.

In addition to these four relatively conventional categories, there are two types of toxins that exist only in a few special worlds, seemingly rare poisons encountered by the wizard who authored the scroll during his travels.

The first is a radiotoxin, which intoxicates nearby life forms through a certain type of radiation, leading to cellular decay. This mysterious toxin is formed naturally by a rare stone named “Radiant Stone” by the wizard.

The second is a parasitic toxin, which is more akin to a microscopic "parasite" rather than a traditional toxin. These parasites proliferate on the cellular barriers of a life form, displaying remarkable adaptability. While they endlessly draw cellular energy for reproduction to the breaking point of the host, they simultaneously create a protective layer over the cells, shielding them from other damage.

The final category, unknown toxins, involves poisons possessing unique capabilities of certain rare creatures, such as through gaze, sound, thoughts, or ideas, leading to intoxicating effects on targets, verging into curse sorcery and mysticism, yet acknowledged by neither.

Nidhogg put down the scroll and curiously asked Peran Ornos, "Mentor, what do you want me to do with this information?"

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Peran Ornos pointed to the sixth type, the parasitic toxin on the scroll, and said, "The foundation of Mixed Venom Body Refinement Sorcery is a parasitic toxin called lymph. You might have some ideas now, right?"

After pondering for a while, Nidhogg reacted with a start, "Could it be that the practitioner is to intentionally infect themselves with this parasitic toxin and then continuously stimulate each cell to strengthen the cell walls through mutual symbiosis?"

"Exactly!" Peran Ornos nodded in satisfaction and added, "A quick learner. Infinite imagination and associative ability are the sources for wizards to gain endless knowledge."

This praise was all directed at Nidhogg.

Nidhogg, however, smiled wryly, "But since lymph is classified as parasitic, it must harm the life form. How do we overcome its harmful aspects to utilize the beneficial ones?"

"There’s no way to overcome it, or rather, there’s no need to overcome it."

Peran Ornos's words stunned Nidhogg, but he knew there was more to come from his mentor.

"Don’t look at me like that. There really isn’t any way to overcome it. The Mixed Venom Body Refinement Sorcery requires a wizard to let these parasites proliferate to their limit inside their body, achieving perfect symbiosis to practice it. The challenges lie in two aspects: the pre-symbiotic adaptation period, during which a wizard is infected by lymph and becomes extremely weak due to the high energy needed for proliferation; and ensuring precise control over the efficacy and quality of the toxin during each comprehensive body stimulation to avoid accidental poisoning in one’s laboratory."

Nidhogg grimaced; this Mixed Venom Body Refinement is truly a dangerous sorcery.

"So... how long does it take to adapt to lymph symbiosis?" Nidhogg ventured to ask.

Nidhogg didn’t bother with how to ensure personal safety during body stimulation since, as a wizard, safeguarding one’s life is a personal responsibility, not anyone else’s concern.

To avoid being poisoned in the lab, the safest bet is to master the efficacy and dosage of the toxins perfectly.

"Adaptation period, you say?"

Peran Ornos chuckled, "Creatures with a physique below 5 have no adaptation period and will soon die from physical collapse. Those with a physique between 10 and 30 will experience localized suppuration without an adaptation phase, and creatures above 30 can’t be parasitized by lymph. As for those between 5 and 10, as long as they survive the three-month period of extreme weakness without being killed by external forces, lymph will proliferate extensively across every cellular barrier, leading to the symbiotic phase."

Nidhogg instinctively took out his black crystal ball and sensed it lightly, with a physique of 5 appearing in his mind.

"Don't worry, you haven’t fully absorbed the rare elements from that sawfish," Peran Ornos reassured, aware of what Nidhogg was thinking.

Pointing to stacks of books on the lab table and rows of white mice in the back room, Peran Ornos continued, "Once you’re infected with lymph, I’ll temporarily confine you here to prevent cross-infection or accidental death. Focus on studying the basic toxin formulations. When the symbiotic phase arrives, I’ll guide you through the full-body cellular stimulation. If you make good progress in the toxin system within two years, I'll consider teaching you other sorceries."

Nidhogg gritted his teeth, confined to this small room for three months?

"Oh, and by the way," Peran Ornos suddenly added, "Wizards practicing physical sorcery don’t enhance their magic to parallel their spiritual power levels through daily meditation. Practicing physical sorcery requires long-distance travel reliant on the body to enhance vitality, strength, and activity to match their physical level. Therefore..."

Peran Ornos waved his hand over his crystal ball, causing a flurry of strange data to appear.

“I will use my authority to assign you the longest route for the mandatory task every two years during your wizard apprenticeship. This task will likely bring you into contact with other wizard apprentices from different academies, making it the most dangerous assignment." Peran Ornos casually remarked.

After a day of Mixed Venom Body Refinement Sorcery knowledge sessions, Nidhogg's physical strength increased again the next day, reaching a level of 6. Peran Ornos retrieved a small vial of purple liquid from a sealed ice chamber and motioned to Nidhogg that this was the fabled "lymph."

Gulp, gulp...

Closing his eyes and gritting his teeth, Nidhogg downed the vial. When he opened his eyes again, Peran Ornos was staring at him incredulously. Curious, Nidhogg asked, "Mentor, what’s wrong?"

"Why did you drink it?"

"Drink it?" An ominous thought crossed Nidhogg's mind, and he turned pale, "Isn't ingesting lymph how it’s done?"

"Uh... ingestion works, but so do skin or respiratory infections..." Peran Ornos’s face, resembling a stitched-up leather ball, barely contained his laughter, leaving one to wonder if it might burst.

At this moment, Peran Ornos curiously asked: "How was the taste?"

Nidhogg smacked his lips thoughtfully, "Initially, it had a foul smell, but now there’s no taste."

Peran Ornos nodded, saying, "It seems the cells in your mouth and nose have begun to be parasitized by lymph, causing sensory impairments. Honestly, this room smells like a dump." With that, the old wizard left the lab without further ado.