Just as Dugu Bo swallowed the herbs, a searing pain burst forth from his abdomen, spreading through every inch of his body. It was the most excruciating agony he'd ever felt—no poison he had encountered before could compare.
His eyes widened in shock, but he couldn't even scream. All he could do was cry out in his heart:
"Was I tricked? But why? I finally made up my mind… and it turns out to be a scam?! Damn it!"
Cheng Ying noticed his reaction and scratched his head awkwardly.
"Oh right, I forgot to mention when the herbs begin transforming your body, it's incredibly painful. The weaker your constitution, the worse it feels. People like me and Bingdi barely feel anything at all.
"If it gets too unbearable, jump into the spring. After taking these two herbs, the extreme yin and yang springs won't harm you anymore." Cheng Ying offered the advice sincerely.
Dugu Bo was already at his limit. He didn't have the presence of mind to judge whether Cheng Ying was lying again, so he just dove headfirst into the blazing yang spring.
But the moment his body hit the water, the pain doubled in intensity. He let out a scream and passed out from the agony. The last thing he heard before losing consciousness was Cheng Ying's voice:
"Once you jump in, you'll black out from the pain. But once you're unconscious, it won't hurt anymore!"
---
When Dugu Bo woke up again, he was lying beside the extreme yin spring. Glancing over, he saw Cheng Ying and Bingdi soaking in the frigid water wearing only their undergarments. Despite the water being over a hundred degrees below zero, the two looked completely relaxed, as if they were enjoying a hot spring.
"Eh? You're awake!" Cheng Ying turned to him while shampooing Bingdi's hair. "Wanna join us for a soak?"
After being tricked twice by this cryptic weirdo, Dugu Bo had grown cautious. He didn't speak or move.
"Ah… right," Cheng Ying followed up, "your martial soul is the Jade Phosphor Serpent. If the water's too cold, you might hibernate."
His words confirmed Dugu Bo's suspicions—if he'd jumped in, he likely would have passed out again from the cold.
Cheng Ying casually finished tying Bingdi's long hair into twin buns, making her look even more like a little loli. Then he turned seriously to Dugu Bo.
"This time, I'm not joking. Will you become my disciple?"
Dugu Bo didn't even hesitate. His poison arts had been completely erased, and this had all been for the sake of taking this mysterious man as his master. Being immune to poison meant nothing if he had no skills left to wield it.
"Don't be so quick to answer," Cheng Ying held up a hand. "I need to make a few things clear first.
"You've seen it for yourself—I'm not exactly human. I don't have much to teach you when it comes to combat. I don't even recognize most of the herbs you know, and when it comes to poison, I may not be more skilled than you.
"What I can teach you is some fundamental knowledge about the nature of matter. Whether you achieve anything with it later on is up to your own effort."
He laid out all the reasons not to trust him in one breath. The more Cheng Ying said, the darker Dugu Bo's face became.
"Would've been nice if you told me all this before you gave me the medicine…"
But it was too late to back out now. Dugu Bo took a deep breath and kneeled down in one motion, performing the traditional three bows and nine kowtows.
"Master, please accept your disciple!"
Cheng Ying's expression became solemn. With a wave of his hand, his soul power turned into a flowing robe. His handsome features and serious demeanor gave him a surprisingly proper, teacherly appearance.
Helping Dugu Bo to his feet, he said, "Rise. Since you've officially become my disciple, I'll give you your first lesson now.
"You've lost your snake venom, so let me start by explaining how different types of snake venom work. That way, you'll know how to harness them if you encounter venomous snakes again."
He started with the basics: neurotoxins, hemotoxins, the differences in symptoms. From there, he dove into mechanisms of action and took the opportunity to introduce human anatomy and cellular biology—most of which he'd picked up from educational shows in his past life. It might not all have been accurate, but it was enough to spark Dugu Bo's curiosity.
At first, Dugu Bo could follow the discussion about symptoms. He even nodded frequently, Cheng Ying's explanations giving him a real sense of clarity.
But as soon as Cheng Ying got into destroying red blood cells, impacting the nervous system, and causing respiratory failure, Dugu Bo started to get lost. And when he reached the part about the chemical makeup of toxins—proteins and polypeptides—Dugu Bo was completely bewildered.
Cheng Ying scratched his head when he noticed Dugu Bo's blank look.
"Yeah, this stuff is probably a bit advanced for you. I'll explain the human body systems and cell theory properly some other time. These are super useful for someone who specializes in poisons—especially for distinguishing between toxins and viruses."
Thinking it over, Cheng Ying realized he might've overestimated how much someone with zero background could take in. Still, Dugu Bo was completely engrossed. He'd spent his whole life immersed in poisons. Even if he couldn't understand it all, Cheng Ying's system of knowledge felt like a beam of light illuminating everything.
Cheng Ying finally stretched and glanced up at the sky. Dawn had broken. He hadn't slept all night but felt no fatigue. He reached over and nudged Bingdi, who was still asleep in the icy spring.
"Time to get up! We're heading back to Tian Dou City! Don't tell me you plan to hole up here for another ten thousand years?"
Bingdi blinked her sleepy eyes open. Fresh out of the water, she looked like a water lily in bloom. Her voice was husky and lazy:
"What's the point of going to Tian Dou City? Haven't I lived like this for hundreds of thousands of years? It's peaceful here. Full of spirit energy. Perfect for cultivation."
"All you do every day is cultivate. Don't you get bored? Don't you want to eat candied hawthorn? Don't you want to sleep in a big comfy bed? Don't you want to go shopping? You won't find any of that here."
Bingdi's face contorted in indecision.
"…How about you go buy those for me?" she muttered.
She wasn't particularly afraid of being discovered in a human city, but living among humans when she'd never done so before… was daunting.
"You think I'm your delivery guy?" Cheng Ying sighed. "If you really don't want to interact with humans, just stay home. There are people like that in human society too—they're called hikikomori, and they live pretty well!"
Bingdi looked genuinely tempted. If she didn't have to deal with humans constantly, maybe it wasn't such a bad idea.
"…Fine. We'll do it your way. But why are you so set on going to a human city?"
"That," Cheng Ying said with a mysterious smile, "you'll understand once you get there. After all, we've got ten thousand years to enjoy life!"
He waved to Dugu Bo, who was still diligently organizing his notes from the lesson.
"Let's go! Back to Tian Dou City!"