After their evening meal, Sereth remained seated beside the fire while Caius gathered the remaining pieces of meat and stored them away. The strange beast core was gone, and although Sereth still did not understand what had happened, he had decided not to dwell on it until he knew more.
There was only one way to determine whether Caius had actually changed: he needed to test him.
Sereth stood and looked toward the open ground beyond the ruined structure. "Caius."
Caius turned toward him. "Yes?"
"Come outside."
Caius followed him into the gray valley. The air was cold, and the ancient ruins stood silently around them. Sereth walked several paces away before turning toward the boy.
"I want to see what the beast core changed."
Caius nodded. "What should I do?"
"Show me the movement technique I taught you."
Caius took a breath and settled his stance, remembering how Sereth had shown him to circulate mana through his muscles and nervous system. Rather than allowing the energy to flow outward, he drew it inward, guiding it through his body in a continuous loop.
His black core responded instantly, and Caius stepped forward.
His movement was remarkably faster than before. He shifted his weight and moved again, his feet barely making a sound against the stone. The circulation of mana lightened his movements, allowing him to change direction rapidly and maintain balance while accelerating.
Sereth watched without speaking as Caius moved again. Then, something strange happened.
For an instant, Caius seemed to disappear. Sereth's eyes followed the trajectory, but his vision lost track of the boy.
He was not completely invisible; Sereth could still sense his presence, but it had become faint and strangely difficult to follow. The aura that had once been easy enough to perceive had almost merged with the surrounding darkness.
Sereth narrowed his eyes and concentrated. Only then could he see Caius clearly again, standing several paces away.
Caius turned toward him. "Did I do something wrong?"
"No," Sereth said.
He did not tell Caius what he had seen. The effect was different from ordinary concealment. The Flow Step was supposed to reduce sound and physical presence by circulating mana through the body, but Caius's black core seemed to be doing something beyond the technique itself, as if the darkness surrounding the boy had accepted him as its own.
Sereth kept the thought to himself; he would need more observation before drawing any conclusions.
Instead, he reached toward the weapons strapped to his back. "Today, I will teach you another form of combat."
Caius watched as Sereth removed two short swords. The blades were slightly curved, their dark metal reflecting the faint light from the distant fire. Sereth held one out toward Caius. "Take it."
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Caius accepted the weapon and tested its weight. "It is lighter than Nightdancer."
"It is supposed to be." Sereth drew the second short sword and held both blades naturally at his sides. "I am going to teach you the dual blade style."
Caius looked at the two weapons. "Is this another secret art?"
"No," Sereth said, shaking his head. "Most dark elf warriors are familiar with this combat form. It is not forbidden, and it is not restricted to any particular house."
"Then why have you never taught me before?"
"Because using two blades does not make a warrior stronger," Sereth explained, raising one sword. "It can make him weaker if he does not understand how to use them. Two weapons mean two points of attack, but they also mean twice the number of movements you must control. A careless swordsman will allow one blade to interfere with the other."
Sereth turned the blade slightly, letting the faint light catch its edge. "The Nyx’ari favor short swords primarily because of our ancestry in the Underdark: narrow tunnels, cramped caverns, and tight spaces where a long weapon would catch on stone or snag in the dark. But do not mistake the weapon for the discipline. The fundamentals of dual swordplay can be applied just as effectively with longer blades, provided the wielder understands the core philosophy."
"And what is the philosophy?" Caius asked.
"Unlike heavy broadswords, which rely on weight, momentum, and brute force to shatter armor, dual swordplay is built entirely upon speed, precision, and leverage," Sereth said. "It relies on lighter, faster techniques. You cannot afford heavy, sweeping swings that leave you open, nor can you rely on raw muscle to overpower a parry."
Sereth stepped forward. "The purpose is not to attack with both blades at once. It is to make one blade create the opportunity for the other."
Sereth demonstrated slowly. His right blade flicked forward in a lightning-fast probe, forcing an imaginary opponent to defend. Before the motion fully finished, his left blade shifted smoothly into the opening created by the first attack, gliding past the defensive guard with minimal movement. Neither blade obstructed the other.
"The first blade controls the opponent's attention and binds their guard," Sereth said as the second blade followed in a tight, fluid thrust. "It attacks where the defense cannot reach."
Caius nodded, tracking the subtle wrists movements. "So the blades work together."
"Exactly. Do not think of them as two separate weapons; think of them as one continuous attack divided between two hands. Whether you hold short blades or long steel, the discipline requires lightness of foot and quickness of hand."
Caius adjusted his grip as Sereth watched him carefully.
"Your right hand should not depend on your left, and your left should not depend on your right," Sereth said. "Each blade must be capable of attacking, defending, and creating an opening instantly."
Caius raised both swords, and Sereth stepped back. "Now attack me."
Caius moved forward. His first strike was intercepted immediately, Sereth's left blade redirecting Caius's sword with a subtle twist of the wrist while his right blade swept toward his shoulder.
Caius twisted away just in time and attacked again, bringing his second blade in a rapid arc from the opposite angle. Sereth blocked it cleanly with a short, efficient movement.
Caius continued pressing the assault. His movements were still rough, but the Flow Step allowed him to shift his position more quickly than before. He changed angles and attempted to attack from both sides, forcing Sereth to move rather than simply stand in place.
Sereth continued blocking, but then Caius suddenly vanished from his vision again for a fraction of a second.
Sereth's eyes shifted. Caius emerged from the darkness at his flank, one blade already moving toward him in a swift, low strike.
Sereth blocked the attack, the impact ringing through the ruins, and Caius immediately brought his second sword around with a rapid wrist snap. Sereth caught that blade as well, locking the weapons together between them.
Sereth looked directly into Caius's eyes. Caius was breathing heavily, but he was smiling faintly.
For the first time since the beast core had disappeared, Sereth saw something that pleased him. Caius was adapting: not merely to the techniques being taught to him, but to his own strange nature.
Sereth released the blades and stepped away. "You are still slow."
Caius frowned. "I thought I was faster."
"You are," Sereth said, lowering his swords. "That is why I am telling you that you are still slow."
Caius looked at him in confusion, prompting Sereth to offer a faint smile. "You have more speed now. What you lack is control."
Caius looked down at the two short swords in his hands.
Sereth raised his blades again. "Again."
Tightening his grip, Caius stepped forward. The training continued beneath the cold gray sky, while deep within the ruins, something unseen continued to watch them.