The training field remained behind with still recent echo of combats. Some students kept commenting in low voices what they had seen, others walked in silence, focused on recovering breath or simply on ordering what occurred. Aku’s group advanced without hurry through academy’s wide hallways, where artificial star’s light entered filtered by translucent panels distributing clarity uniformly.

Gerald walked a bit behind, adjusting glasses every few steps, still with irregular breathing.

"I don’t know how you can fight like that first thing..." he murmured, rubbing neck. "My body’s still in survival mode..."

Bīng Xuě stretched while walking, rotating shoulders with ease.

"Been good. Though we could’ve continued a bit more."

Gerald looked at him sideways.

"No, thanks. I’ve had enough ’good’ for today."

Aku didn’t intervene. His pace was constant, gaze fixed ahead. Combat had left useful information, but was already archived in his mind, integrated as another piece of data within continuous analysis.

Theory classroom was in elevated section of main building. Upon entering, amphitheater arrangement imposed itself again: ascending rows of seats, each with integrated work surface, and at front wide area where professor could move freely. Floating screen was already active, showing series of incomplete diagrams, as if explanation had begun before they arrived.

Alfarius Trimegistus was already there.

Standing, back straight, hands interlaced at waist height. His uniform maintained sober tone, more functional than ostentatious, with clean lines and minimal details. Glasses reflected screen’s light, partially hiding gaze until he turned head slightly toward entering students.

"Take your seats."

Didn’t raise voice.

Wasn’t necessary.

Classroom filled in few seconds. Aku again occupied position in rear part, with complete view of space. Bīng Xuě sat beside him, resting elbow on surface with relaxed attitude. Gerald took bit longer to settle, releasing sigh while dropping into seat.

"Theory class... good... this I can survive..."

Alfarius waited for murmur to extinguish.

Then took step forward.

Screen behind him changed.

Enlarged cellular structure appeared, accompanied by tissue layers represented in cross sections.

"We continue with containment methods," he said. "Focused on rank D to B entities."

Stopped instant.

"Also known as structural propagation infections or field parasites."

Image changed.

Now showed partially decomposed humanoid figure, with altered tissue zones.

"Basic example: zombie-type necrotic infection."

Gerald leaned slightly forward.

"Okay... this sounds interesting..."

Alfarius continued without varying tone.

"Unlike what many worlds believe, these organisms don’t function through classic reanimation. There’s no ’life after death’ in traditional sense. What you observe is parasitic biological system replacing host organism’s critical functions."

Image zoomed in.

Internal tissue layers showed.

"Process begins with external agent infiltration, generally of chaotic origin, altering cellular activity at metabolic level. This agent introduces pseudo-organic structure acting as control nucleus."

Network of filaments appeared on screen, extending through body.

"These filaments progressively replace peripheral nervous system. Don’t transmit electrical impulses as normal neurons would. Function through chaotic energy gradients, generating simple motor responses based on external stimuli."

Bīng Xuě tilted head slightly.

"So they don’t think?"

Alfarius negated.

"Not in cognitive sense. They respond."

Image showed how filaments connected with muscle fibers.

"Muscle doesn’t cease to exist. Remains functional tissue. But activation no longer depends on conventional neuronal signals. Parasite induces direct contractions, using body’s internal energy reserves."

Gerald half raised hand.

"But... if they’re dead... where do they get energy?"

Alfarius turned gaze toward him.

"They’re not dead in complete metabolic sense. Parasite maintains basic processes active. Additionally..."

Image changed.

Showed digestive system section.

"Many of these organisms develop ingestion mechanisms. Not for traditional nutrition, but to acquire biomass parasite can decompose and reuse."

Screen showed how ingested tissue decomposed at cellular level.

"System doesn’t digest like healthy organism. Fragments. Redistributes. Converts matter into usable energy within own network."

Aku observed in silence.

Explanation wasn’t new to him in concept, but detail level was useful.

Alfarius continued.

"Main problem isn’t individual."

Image expanded.

Now showed multiple figures.

"It’s propagation."

Simulation began.

Infected individual bit another. Agent transferred.

"Transmission vector usually biological: fluids, direct contact, inhalation in some cases. Agent penetrates bloodstream and begins replication."

Screen showed process at microscopic level.

"Once inside, parasite releases enzymes degrading cellular membranes, allowing expansion. Within hours, nervous system begins failing, and control passes to parasitic nucleus."

Gerald frowned.

"Okay... that’s worse than I thought..."

Alfarius didn’t react.

"Containment methods."

Image changed again.

Urban environment appeared.

"Fire is most common method."

Burned zones showed.

"Reason is simple. Extreme heat denatures proteins composing both host tissue and parasite. Without functional protein structure, system collapses."

Screen showed how cells decomposed under high temperatures.

"However, this isn’t always efficient. In enclosed or densely populated environments, fire use can generate more collateral damage than benefits."

Image changed.

"Alternative: metabolic interruption."

Chemical compounds showed.

"Some worlds have developed agents blocking ATP production in infected cells. Without energy, parasite can’t maintain muscular activity."

Bīng Xuě raised eyebrow.

"Doesn’t that kill host too?"

"Host is no longer recoverable in most cases."

Brief silence.

Alfarius continued.

"Another variant: environment control."

Screen showed ground.

"In expansive-type infections, parasite doesn’t limit itself to body. Extends to terrain."

Image showed black roots growing under surface.

"Some zombie systems develop underground networks. Parasitic mycelium connecting multiple bodies."

Gerald leaned more forward.

"Like fungus?"

"Similar."

Image showed how filaments extended through ground.

"Parasite uses terrain as transport and storage medium. Can redistribute biomass between bodies, repair damage, even coordinate basic movements between multiple units."

Aku narrowed eyes slightly.

That was more interesting.

"In these cases," Alfarius continued, "containment doesn’t limit itself to individuals. Treating ground is necessary."

Screen showed process.

"Methods include deep incineration, broad-spectrum antifungal agent application, or terrain pH alteration to destabilize network."

Simulation showed how mycelium collapsed.

"Without network, individual bodies lose coordination and efficiency."

Bīng Xuě rested chin on hand.

"So they become easier to destroy."

"Correct."

Screen changed once more.

Larger creature appeared, with multiple limbs.

"Rank B."

Figure moved with more coordination.

"Here, parasite has developed more complex central nucleus. Capable of processing basic information and coordinating multiple bodies or structures."

Image showed bright nucleus inside.

"In these cases, nucleus elimination is priority. While it exists, network can regenerate."

Gerald sighed.

"Okay... that already sounds like video game boss..."

Alfarius ignored comment.

"Key point is understanding biological system behind entity. Without that knowledge, any containment attempt is inefficient."

Screen stopped.

Classroom remained silent few seconds.

"This is just foundation."

His gaze swept room.

"In next part, we’ll address more complex variants and advanced intervention methods."

Hadn’t finished.

And information was barely beginning to become really dangerous.