Winter on the sea outside the Tower of Heaven always brought a lethal dampness into the stone cells. For the slaves, this was the season of "Nature's Cleansing," where those whose lungs were already filled with crystal dust would usually succumb to the cold.
In cell 402, the most dominant sound was no longer the heartbeat of the machinery or the footsteps of the guards, but the sound of Nana's dry, heavy, and racking cough.
Ren Chicle sat beside Nana's bed—a thin, worn-out pile of burlap sacks. In his hand, he held a wooden bowl filled with water that he had purified using a bit of his magic energy to remove the toxic metallic taste.
"Drink, Nana," Ren whispered. His voice, usually flat, now contained a tremor he couldn't hide.
Nana tried to sit up, but her emaciated body seemed to have lost its gravity. Her skin had already turned a shade of gray, nearly transparent to the point where her blue veins were clearly visible.
"Thank you, child... but water cannot fix an old machine."
Ren stared at Nana with an intense gaze—the gaze of Analysis. In his mind, he no longer saw Nana as a human being, but as a collapsing biological system. He could see organ failure, blockages in the airway due to Ethernano radiation, and a heart beating with an irregular rhythm.
Why can I see the damage but cannot reconstruct it? Ren clenched his fist until his nails dug into his palm.
"I will find the cure," Ren said firmly.
"Vane said there are medical supplies in Sector 2, where the priests of Zeref are. They have healing Lacrima."
"Don't, Ren!" Nana grabbed the boy's hand with what was left of her strength. Her grip was weak, but her eyes radiated an overwhelming fear.
"Sector 2 is a dragon's den. If you are caught there, they won't throw you into the sea. They will strap you to an experiment table. You are the future, Ren... do not trade your life for the mere days I have left."
"The future means nothing if you are not there to see it!" Ren stood up, his voice rising an octave.
The air inside the cell suddenly grew hot. The Lacrima in his pocket glowed for a moment.
"Logic dictates that your survival is my highest priority. You are the only variable that gives me a reason not to become a monster like them!"
Nana fell silent, staring at the fire of anger and sorrow in the six-year-old boy's eyes. She realized that Ren's love had turned into a dangerous obsession.
"Ren... listen to me. Death is not a failure. It is a part of the equation that you cannot change."
That night, as Nana slept in a violent fever, Ren slipped out. He moved like a shadow between the gaps of the hot steam pipes. His mind worked at the speed of thousands of calculations per second. He mapped the fastest route to Sector 2's logistics warehouse, calculated the intervals of the guards' searchlights, and monitored the vibrations in the air to detect human presence.
At a dark intersection, he ran into Kael.
"You're crazy, Ren," Kael whispered, his face pale under the glow of the blue crystal.
"Sector 2 is guarded by mages. Not just guards with whips. You will die."
"I need a catalyst," Ren said, his eyes flashing coldly.
"Anything that can stabilize the human cell structure. Kael, if you help me by opening the door and distracting the guards at the steam gate, I will owe you my life."
Kael swallowed hard. He saw the desperation on Ren's face, something far more terrifying than Krov's whip.
"Alright. I'll go open the door. But if in ten minutes you do not return, I'm leaving. I don't want to die for an old woman who is already dying."
Ren didn't answer. He just kept moving with Kael. After a few moments of dodging guards, Ren and Kael arrived in front of Sector 2.
Ren touched the steel door of Sector 2. This door had a dual mechanism, operated by magic and a physical key. The key was used to unlock it, and channeling magic energy opened it.
"Kael, your turn," Ren said.
Kael nodded.
Click. Kael unlocked the door.
"I'm leaving, Ren. Good luck."
"Yeah."
Ren then touched the door, and with a slight channel of magic, he pushed it, making it open soundlessly.
Inside the warehouse, the sharp smell of antiseptic assaulted his nose. Ren found rows of liquid Lacrima bottles. He searched for the green one; green meant life, green meant regeneration.
However, as he touched the bottle, he realized something bitter. This liquid only worked on physical wounds. It could not heal systemic damage from years of Ethernano radiation. This was medicine for soldiers, not for slaves already broken from the inside.
Not enough. This is not enough!
Ren dropped the bottle to the floor. He began searching for literature, magic scrolls, anything. He found an ancient book with a single-eye symbol, the mark of dark magic. Inside, there was a chapter on "Life Transmutation."
"To revitalize a dead structure, pure energy from an equivalent subject is required..."
Ren's hands trembled. His intellect told him this was a logical solution: an exchange of energy. But his conscience, Nana's voice in his head, screamed that this was true darkness.
Ren returned to the cell before dawn broke, empty-handed and with a heart heavier than the tower's stones. He found Vane standing in front of their cell door with his head down.
"She's looking for you, Ren," Vane whispered.
"Hurry."
Ren ran inside. Nana looked smaller than ever, as if the weight of this world was crushing her into nothingness.
"Ren..." Nana's voice was barely a whisper of wind.
"You came back..."
Ren fell to his knees beside her.
"I'm sorry, Nana. I couldn't find anything. I... I have the smartest brain here, but I can't save you. This knowledge is useless! This power is garbage!"
Nana smiled, a smile so peaceful it made Ren sob for the first time since he was born.
"You're wrong, child. You saved me from the day you were born. You gave me a reason to survive for six extra years. That is a magic greater than anything in this tower."
Nana reached for Ren's face, wiping the tears from the boy's cheeks with her rough thumb.
"Do not seek power to fight death, Ren. Seek power to protect the life that remains. Promise me... do not let this Tower turn you into someone cold."
"I promise, Nana. I promise," Ren broke down crying.
Nana's breathing became very shallow.
"Look... Ren... the sun... I can feel it..."
The light in Nana's eyes dimmed for the last time. Her hand fell from Ren's cheek, leaving behind a warmth that slowly grew cold. Outside, the forced labor bell began to ring, calling thousands of souls back to suffer, but for Nana, that suffering had ended.
Ren fell silent. He didn't scream. He didn't destroy the cell. But inside him, something truly broke. The sadness did not disappear; it crystallized into an incredibly sharp resolve.
He realized one most logical thing: in this cruel world, kindness like Nana's is a fragile light. That light will always go out unless there is someone with enough power to protect the flame from the storm.
I need more than just intelligence, Ren thought as he stared at the rigid body of the only family he had.
That night, Ren did not sleep. With Nana's last piece of charcoal, he wrote a new equation on the cell wall. This time it wasn't arithmetic. It was a plan to destroy every single stone in the Tower of Heaven.
Vane and Kael stood at the cell door, staring at Ren who now looked different. The aura around the boy was no longer just heat, but felt like a pressing energy field, ready to explode.
"Vane, Kael," Ren's voice was cold, yet filled with authority.
"Our escape will not happen in a matter of years anymore. I have recalculated the risks."
"When?" Kael asked in a trembling voice.
Ren turned his head, his clear eyes now reflecting the blue glow of the crystal in a terrifying way.
"As soon as I master the secret behind this Ethernano. This tower will not be a grave for us. It will be the place of my true birth."