After Anna left, the taut string in the room seemed to snap.

  The immense fatigue following intense concentration, coupled with the dull ache of spiritual overextension, washed over Erika like a tide. Leaning against the cold wall, he had intended to keep puzzling over the stolen fragments of conversation, but his eyelids were simply too heavy to lift.

  His consciousness struggled for a few moments in a vortex of cold terms—'specimen mutation', 'energy feedback', 'three cycles'—before being irresistibly pulled into a dreamless darkness.

  This time, it wasn't a terrifying emptiness. It was a deep, restorative sleep.

  He didn't know how much time had passed when another faint sound came from outside the door. It was even more cautious than Anna's last visit.

  Erika jolted awake, his heart seizing. His hand instinctively groped the bed beside him. Finding nothing, he remembered he had no weapon.

  The door cracked open.

  Anna's small head peeked in. She was clutching a thick book wrapped in worn, dark blue cloth, its corners frayed. Seeing Erika sitting up, she visibly relaxed, slipped inside like a nimble fish, and quickly closed the door.

  "You're awake!" she whispered, a hint of triumph in her voice after completing her dangerous task.

  She carefully placed the book on the bed.

  "I found it! This is it, An Analysis of Spiritual Resonance. I snuck it out when the overseeing Sister wasn't looking... We have to be quick, though. I need to return it before evening prayers."

  Erika pressed his fingers to his still-throbbing temples, his gaze falling on the dark blue bundle. A vessel of knowledge—it felt both precious and incredibly dangerous now.

  "Thank you, Anna," he said sincerely, then gestured to his head. "I'm feeling better. Just still a bit... empty."

  Anna nodded vigorously in understanding. She carefully unwrapped the bundle, revealing a heavy tome with yellowed pages. It smelled faintly of mildew and old ink. The text was written in a slightly ornate common script, interspersed with abstract symbols and complex diagrams.

  "Look here," Anna said.

  Having clearly browsed it on her way back, she expertly flipped to a middle page and pointed to an illustration of concentric ripples.

  "The book says our spirit is like calm water. Every thought creates 'ripples'. 'Mind-voice' is about actively controlling those ripples, making them travel only in a specific 'direction'."

  Erika leaned in closely.

  Next to the diagram were dense annotations explaining the effects corresponding to different mental 'frequencies', and how to adjust one's own mental 'amplitude' and 'wavelength' through deep meditation.

  "It says the purer the spirit, the sharper the focus, the more 'stable' the ripples created," Anna continued, her expression dead-serious, like a tiny scholar. "That makes them less likely to suffer interference by other ripples, and they can more accurately reach the target 'water'. But if your own spirit is chaotic, or there are many powerful 'ripple sources' nearby, it's easy to... get cross-talk."

  Erika listened quietly, his mind racing.

  He cross-referenced Anna's explanations with his own terrifying experience earlier. Frequency, amplitude, wavelength, interference... These words provided a framework of near-physical laws for understanding that mysterious mental force.

  It fit his way of thinking far better than Wolfgang's dogma-filled, abstract metaphors.

  "So," Erika mused, his finger unconsciously tracing the ripple pattern on the yellowed page, "to avoid interference, or... to 'listen' better to a specific frequency, you first need to make your own 'water' as calm as possible. And then... you adjust yourself to 'match' the amplitude and wavelength of that frequency?"

  This text was taken from Royal Road. Help the author by reading the original version there.

  "Match?" Anna blinked, intrigued by the term.

  She looked back at the book, thought for a moment, then nodded firmly.

  "Mhm! The book doesn't use the word 'match' exactly, but it says the receiver finds it easier to catch clear 'messages' if they are in a 'resonant' state. Resonance... that must be what you mean by 'match', right Erika?"

  Resonance. Match.

  The words were like keys unlocking a heavy iron door in his mind.

  His earlier passive reception of the black-clad Clerics' conversation hadn't been an accident. It might have happened precisely because, in his state of extreme fatigue and mental emptiness, he had inadvertently allowed his own mental frequency to achieve a brief 'resonance' with that high-intensity, icy communication channel!

  It wasn't a brute mental intrusion. It was more like... precise tuning.

  The realization made his heart race. If he could actively master this 'tuning' technique, even at its most basic level, did it mean he could acquire an extremely dangerous, yet potentially powerful, eavesdropping tool within this information prison?

  He looked at the ancient text, then at the utterly trusting, guileless Anna sitting before him.

  A complex emotion welled up in his chest—profound gratitude, tangled with a thread of indescribable guilt. He was using her kindness and knowledge to plot something that could drag them both into a bottomless abyss.

  "Anna," he said softly, his voice slightly hoarse, "This book... could you tell me more about how to practice 'resonance'? And how do you know if you're actually in a 'resonant' state?"

  Anna, completely unsuspecting and believing Erika was simply eager to learn, eagerly turned to another page. Pointing to meditation diagrams and breathing rhythm instructions, she began explaining earnestly.

  Erika listened intently, carving every single detail into his mind.

  Outside, the Sanctum's holy light continued its indifferent, oppressive shine. But within this small, isolated cell, a secret initiation into frequencies, silence, and impending storms was quietly underway.

  As Anna explained, Erika found the abstract concepts of 'frequency' and 'amplitude' becoming clearer in his perception.

  He could even vaguely connect them to the faint energy flow hidden deep within him, and the lingering warmth of the Auric Mark on his hand. A bold, reckless idea sprouted in his mind.

  If 'Mind-voice' relied purely on mental strength, wouldn't someone like him—with a recently depleted spirit but inherent 'special' energy qualities—never be able to use it effectively?

  He decided on an extremely minute, cautious experiment.

  While Anna explained how to stabilize the mental 'water' through breathing, he didn't follow her instructions completely. Instead, he diverted a tiny sliver of his will. He carefully guided the faint, almost negligible flow of Auric energy within him—the one that had not yet fully recovered—and attempted to... attach it to the 'mental ripples' Anna described.

  At first, nothing changed.

  But then, he finely tuned that faint thread of golden energy to nearly synchronize with the frequency required for 'stable transmission', just as Anna had explained.

  Hum...

  A strange, terrifying sensation arose!

  His originally weak, easily dispersed mental 'ripple' felt as if it had been injected with an incredibly fine yet resilient 'skeleton'. It instantly became stable and condensed!

  What shocked him more was that in that exact moment, he could vaguely sense the subtle fluctuations of Anna's own mental 'water'. He could almost 'hear' the focused intensity of her teaching thoughts.

  It was no longer one-way listening. It was a fuzzy, two-way perception!

  The range of this perception also seemed to far exceed the limits Anna had stated in the book. He felt his extended mental 'antennae' could reach further, as if the energy skeleton was artificially amplifying and projecting his mental signal.

  However, this wondrous, god-like feeling lasted for less than a heartbeat.

  "Guh!"

  A wave of intense vertigo and the familiar, blinding sting between his brows struck him like a hammer. The Mark on his left hand flared with a brief, sharp, agonizing burn!

  The thread of energy attached to the mental ripple instantly dissipated, and the faint connection he'd just established snapped violently.

  "Erika? What's wrong?!" Anna stopped her explanation immediately, terrified as she watched the color drain completely from his face.

  "Nothing... it's nothing," Erika forced down the churning, nauseating discomfort in his chest and the stabbing pain in his skull. He managed a weak, unconvincing smile. "Just a bit... tired. Anna, I think I understand the core principles now. Thank you so much."

  He glanced at the ancient tome.

  "The book... you should take it back now. It wouldn't be good if it's discovered missing."

  He couldn't continue the lesson. The brief attempt, though painfully short-lived, had revealed a terrifying and alluring possibility: energy could bypass the natural limits of mental strength, forcibly expanding the boundaries of 'Mind-voice'.

  But it was undoubtedly walking a tightrope over an active volcano. Each attempt could trigger a more violent physical backlash, or worse... it could trip the invisible alarms in the Creed's monitoring network.

  Seeing he truly looked unwell, Anna, though a bit disappointed to end the lesson early, nodded obediently. She carefully re-wrapped the book in its dark blue cloth.

  "Then rest well. I'll check on you later."

  Hugging the bundle tightly to her chest, she slipped away as silently as she had come.

  Alone in the dim room, Erika pressed a trembling hand to his still-aching forehead.

  But beneath his fingers, his hollow eyes shone with an unprecedented, dangerous light.

  Energy-assisted... Two-way communication...

  This was no longer simple, passive eavesdropping. It meant... he might be able to actively do more in this prison.

  But at what cost? Where would this power, seized by crossing forbidden boundaries, ultimately lead him?