The disappearance of Medb and the recovery of the Holy Grail did not bring peace to the throne room. Instead, they unleashed a beast stripped of its reason for being, but not of its lethality. Cu Chulainn Alter, now deprived of the constant flow of corrupting energy from the Grail and the voice of his "queen," did not fade away. He remained there, in the center of the shattered hall, like a nightmare statue made flesh. His breathing, once a bestial growl, had become a slow, deep hiss, like steam escaping a pressurized boiler. His red eyes, without the spark of distorted obedience, now shone with a purely predatory intelligence, fixed on Leonel and his Servants.
He was not a lightweight. He was a wall. A wall of muscle, corruption, and a curse that seemed woven into the very essence of his Saint Graph. The first moments after Medb vanished confirmed it.
"Now! While he's disoriented!" ordered Leonel, and a coordinated attack was launched against the beast.
Jeanne Alter, with black fire still burning on her sword, charged from the left. Nero Bride, from the right, her white sword tracing a perfect arc. Mordred, from the front, with Clarent roaring with energy. Three simultaneous attacks, from three angles, executed with the synchronization only practice and the Master's bond could allow.
It was then that Leonel and everyone present saw the true horror of Cu Chulainn Alter.
The being did not flinch. It did not dodge. It simply... changed.
A subtle glow, like that of red-hot metal seen through a curtain of smoke, ran across his body for a fraction of a second. When the weapons were about to impact, his skin, where Jeanne Alter was aiming, seemed to turn the color of cold ash, and the black fire extinguished on contact as if it had struck absolute barrenness. Where Nero Bride attacked, the corrupt flesh hardened until it acquired the sheen of polished obsidian, deflecting the blade with a dry crack. And against Mordred's frontal attack, his body seemed to turn liquid for an instant, absorbing and dissipating the force of the impact in a wave of darkness that forced the Saber back.
It was like hitting a ghost that chose in what way to become solid at the precise moment of impact.
"Fall back!" shouted Leonel, his heart freezing in his chest. The Servants retreated, confused and frustrated.
"Analysis," Leonel demanded, his mind already working at full speed with Tezcatlipoca.
The Persona, impassive but intensely focused, projected data into Leonel's consciousness. "The subject exhibits a capacity for real-time adaptive mutation. It is not a fixed passive resistance. It appears to respond to the nature of the imminent attack. Upon perceiving fire, it develops extreme thermal immunity. Upon perceiving slashing weapons, it increases dermal hardness. Brute force attacks are dissipated via a variable density transformation."
"Weakness? There has to be a weakness," insisted Leonel, watching as Cu Alter began to advance, his pace heavy but relentless, his corrupt spear dragging on the ground and leaving a furrow of molten stone.
"Attempting to determine a pattern..." Tezcatlipoca scanned, seeking inconsistencies in the energy flow. "Moment of change: 0.05 seconds before impact. Origin: an automatic reaction of the Saint Graph, possibly an innate skill or a curse granted by the Grail. Potential weakness... undetermined. The defensive parameter mutates to counteract the specific threat."
Leonel saw it in action again and again. Kiyohime unleashed her blue flame breath; Cu Alter's skin became scaly and refractory. Artoria Alter tried to freeze him with Rhongomyniad's cold; his body emitted residual heat that evaporated the ice. Billy fired a magical bullet; the flesh at the point of impact turned gaseous and reformed instantly.
It was like fighting a flesh-and-blood riddle. Every solution they devised was invalidated the moment it was applied. The Servants, guided by Leonel through Tezcatlipoca, executed complex maneuvers, combined attacks, ambushes. They scratched the surface, left superficial marks that seemed to slowly close, but no decisive blow. And with each failed attempt, with each transformation of Cu Alter, Leonel felt a drain. Not just on his magic reserves, which flowed to sustain his Servants in this high-octane combat, but a mental drain. The burden of processing Tezcatlipoca's information, of devising strategies in microseconds, of coordinating nine Servants (ten with Tamamo as support) against an enemy who constantly rewrote the rules, was exhausting.
Cold sweat soaked his clothes. A dull pain began to throb behind his eyes. Through Tezcatlipoca's shared senses, he saw how his Servants also began to show signs of fatigue. Jeanne Alter was breathing heavily, her fury no longer enough. Mordred's arm was trembling from the impact against the adaptable defense. Even Nightingale, observing with her usual coldness, had a slight furrow on her brow in a rare gesture of intense concentration.
"Master, our energy reserves are depleting at an accelerated rate," Tamamo informed him, her voice tense through the link. "If we continue like this, I won't be able to maintain the reinforcements for much longer."
Leonel looked at Cu Chulainn Alter. The beast seemed unperturbed. Its energy, though no longer fed by the Grail, was deep and monstrous. This battle could not be won by attrition. They would fall first.
A desperate decision took shape in his mind. It was a huge risk, but his dependence on Tezcatlipoca, though vital, was also a luxury he could no longer afford. The Persona's constant analysis consumed a significant part of his magic. He had to think for himself. He had to find the pattern with his own eyes, his own mind.
"Tezcatlipoca," he ordered, his mental voice a weary whisper. "Pull back. Maintain only the basic communication link. Conserve energy."
A wave of surprise, almost concern, emanated from the Persona. "Leonel, without my analysis, the error rate in your perceptions will increase by 400%. The risk is extreme."
"I know. But if we run out of magic, we're dead. Do it."
The imposing figure of Tezcatlipoca faded from his side, becoming an ethereal, silent presence, just a thread in his mind for urgent communications. Suddenly, Leonel felt incredibly alone and vulnerable. The world of combat, once seen with the hyperbolic clarity of Tezcatlipoca's radar, was reduced to his own human senses. Sound was chaos, Cu Alter's movements were blurs, the information, incomplete.
But he also felt relief in the flow of his magic circuit. The constant drain lessened. He had time. Maybe ten minutes. Maybe less.
He took a deep breath, forcing his mind to calm down. He no longer had processed data. He had to observe. Like a blind chess player, he had to reconstruct the board in his head.
He fixed his gaze on Cu Chulainn Alter. He ignored the shouts of his Servants, the din of impacts. He concentrated on the moment of change. Every time a Servant attacked, just before the attack connected, there was that subtle glow. He already knew that. But now, without Tezcatlipoca's interface, he saw something more. It wasn't a uniform glow. It was as if certain parts of its body lit up with more intensity depending on the attacker.
When Jeanne Alter attacked with fire, the glow concentrated on the torso and arms, taking on a dark red hue.
When Mordred attacked with brute force, the glow went to the legs and core, turning purple.
When Kiyohime used her spiritual fire, the glow was bluish and spread like a net under the skin.
And then, after the glow, the transformation. And after the transformation, when the attack was neutralized, the glow faded, and for a very brief instant—a second? less?—Cu Alter's skin returned to its "base" state, pale and corrupt, before the glow of a new attack began.
It wasn't that he had no weaknesses. It was that his weakness changed. It transformed into the strength needed to counter the last threat. But in that instant of transition, in the moment when the "strength" against fire dissipated to make way for the need for a new defense, there had to be a window. A window where he was vulnerable to something that wasn't what he had just blocked.
And then, the final piece of the puzzle clicked. It wasn't just about the type of attack. It was about the Class. Cu Alter didn't adapt to the element (fire, ice, force), he adapted to the nature of the Saint Graph's threat. He became resistant to Berserker attacks (Kiyohime), then to Saber attacks (Mordred, Nero), then to Avenger attacks (Jeanne Alter). But the adaptation wasn't instantaneous for everything. It was specific.
The strategy wasn't to find a fixed weakness. It was to force a cycle. A cycle of adaptations that would leave him exposed, even for a fraction of a second, to the right attack at the right time.
"Everyone, listen to me!" shouted Leonel, his voice hoarse but charged with a new certainty. Tezcatlipoca's link transmitted his urgency to all. "Forget combined attacks! We need rotation! By Class!"
He explained quickly, between gasps, as they dodged a spear strike that shattered a column beside them. "Attack one at a time! In a specific order! Berserker first! Kiyohime, now! Just one strong attack and then fall back!"
Kiyohime, though confused, obeyed. With a cry, she blasted her blue flame breath against Cu Alter's chest. The blue glow ran across the beast, and its skin became scaly and refractory. The fire dissipated with no effect.
"Now, Saber! Mordred, attack with brute force, now!" ordered Leonel, counting mentally. One, two...
Mordred charged, Clarent held high. The moment her sword descended, the glow on Cu Alter changed from blue to purple, concentrating on his arms to harden them against the blow. The impact was deflected, but Leonel wasn't watching that. He was watching the beast's body. Three, four...
"Avenger! Jeanne, black fire, now!"
Jeanne Alter, catching on, launched a concentrated spear of black flames. The glow on Cu Alter flickered, changing from purple to a dark red to counteract the hatred-fueled fire. Five, six...
And then, on the seventh second after Kiyohime's attack, Leonel saw it. The dark red glow of resistance to the Avenger was beginning to fade to make way for... what? What would he adapt to now? The cycle would reset. But in that flicker, in that transition, Cu Alter's skin returned to its base pallor.
"Lancer! Artoria, now! Your spear, absolute cold, AT THAT POINT!" Leonel yelled, pointing not at Cu Alter in general, but at the center of his chest, where the glow was dissipating.
Artoria Alter, without question, thrust Rhongomyniad. The black spear, wreathed in a cold that made the air congeal, shot out like lightning. It wasn't an area attack. It was a precise, surgical thrust.
Cu Chulainn Alter, his adaptation system still processing the change from the "Avenger" attribute to whatever came next, couldn't react in time. The tip of Rhongomyniad struck his chest, just as his defense was at its lowest. The sound wasn't of metal against a fortress, but of shattering ice and torn corrupt flesh. A genuine grunt of pain, not fury, escaped the beast. A black, frost-rimmed crack appeared on his chest, from which dark vapor emanated.
It worked!
But it wasn't enough. The wound was serious, but not mortal. And now Cu Alter was alert, enraged, and his adaptation cycle would accelerate, become less predictable.
"The cycle is accelerating! The window is shorter!" shouted Leonel, his mind racing at full speed. Now he had to coordinate not only the order, but the timing with nanosecond precision. It was no longer 10 seconds. Maybe 7. Maybe 5.
"Mash, Nightingale, with me!" Mash positioned herself in front of him, her shield ready for any stray attack. Nightingale moved to his side, her analytical eyes scrutinizing him, not the enemy.
"Symptoms of severe magical exhaustion, increased heart rate, cognitive dehydration," she diagnosed in her flat tone. She pulled a syringe from her apron. "Short-term stimulant injection and glucose concentrate. It's not a treatment, it's a patch. It will give you ten minutes of lucidity before collapse."
"Do it," said Leonel, not taking his eyes off the combat. He felt the prick in his neck, followed by a wave of artificial clarity and nervous energy. The headache faded, replaced by a feverish hyper-lucidity.
With his mind now forced to function at maximum capacity, he restarted the dance. "Changing order! Archer, now! Billy, a shot to the head! Then Caster, Tamamo, a slowing curse! Then Rider...!" He realized he didn't have an offensive Rider. "Jeanne Alter, again, but change the angle!"
It was a hell of micro-management. Leonel was the conductor of an orchestra where each musician played a different instrument at a tempo that constantly changed, and a note out of time meant the death of a band member. His Servants trusted him implicitly, moving like extensions of his will, attacking and retreating at the exact instant.
Over and over, they forced Cu Alter's adaptations. Fire, then force, then curse, then cold, then fire again. Each cycle, Leonel sought the window, that flicker of vulnerability, and launched the attack of the Class or attribute that hadn't been used in the last few seconds of the cycle, the one Cu Alter's adaptation wasn't prepared to block.
It was exhausting. Even with the stimulant, Leonel felt his mind melting. Every order was a heart-wrenching calculation. Every second, an eternity.
Cu Chulainn Alter, cornered by this relentless and counterintuitive strategy, roared in frustration. He was covered in wounds: a cold burn here, a crack from brute force there, a mark of corruption from a curse elsewhere. He bled darkness and his movement was becoming slower, clumsier. But he was still lethal. A single error, and his spear would pierce anyone.
The hall was now a landscape of craters, broken columns, and collapsed walls. The battle had spread, turning Medb's throne into an arena of destruction.
Leonel, his shirt soaked in sweat, eyes bloodshot, remained standing, leaning on Mash to avoid falling. Nightingale was by his side, ready with another syringe, but knowing another dose could stop his heart.
"He's... almost..." Leonel gasped, watching as Cu Alter staggered, his adaptation cycle now a chaotic, erratic flicker, like a machine breaking down. The beast could no longer keep up. The strategy had worked. It had exploited the very nature of his power against him.
"Last cycle..." he murmured. "Everyone... ready for the Noble Phantasm... on my signal..."
The light in his eyes was beginning to blur. The stimulant was wearing off. But he still had one last order to give. The one that would end this.
The dance of the changing specter was coming to an end, and the master choreographer, on the verge of collapse, prepared the final dance.