The next floor was different. There was no grand arena, no endless army, no beautiful trap. The portal from the gray plain of silence took them to a single, circular room made of smooth, polished black stone. It was about the size of a large temple, and completely empty. In the very center of the floor, there was a circle of glowing white runes. In the very center of the ceiling, directly above it, was another circle of runes, glowing with a dark, deep blue light.

The air here was still and heavy, like the moment before a lightning strike.

"This is it," Alex said, his voice quiet in the huge, quiet room. "The last guardian."

Saeko felt her heart beat faster. This felt final. "What is it?" she asked, her hand on her katana.

Before Alex could answer, the two circles of runes—the white one on the floor and the blue one on the ceiling—flared with a light so bright it hurt their eyes. Beams of pure energy shot from both circles and met in the middle of the room.

Where the beams met, a figure started to form. It wasn't made of flesh or bone. It was made of solidified light and shadow. It was human-shaped, but taller than Alex, and its body seemed to be constantly shifting. One half of its body glowed with the harsh, white light of the floor runes. The other half was made of the deep, swallowing blue shadow of the ceiling. Its face was blank, with no eyes, no mouth, just a smooth surface. In its hands, it held two swords that were made of the same shifting light and shadow.

It was the Sentinel. The final defense of the Frozen Sepulcher.

It didn't roar or scream. It just stood there, and a voice echoed in their minds, cold and without emotion. INTRUDERS. THE SEPULCHER ENDS HERE. YOUR STRENGTH WILL BE ADDED TO THE DEFENSES.

"Well, it talks," Saeko muttered, getting into her fighting stance. The wind began to pick up around her.

Alex drew his own sword, the dark steel looking very real and solid compared to the Sentinel's ghostly weapons. "It's a reflection," he said, his eyes narrowed. "It uses the energy of those who come here. It will try to fight us with our own power."

As if to prove his point, the Sentinel moved. It was fast—blindingly fast. It came at Alex first, its white sword swinging down in a move that was a perfect copy of one of Alex's own overhead strikes, but made of searing light.

Alex met it with his own blade. The crash sounded like thunder in the small room. Sparks of dark energy and white light flew everywhere.

At the same time, the Sentinel's shadowy blue sword shot out toward Saeko without the creature even looking. A crescent of dark energy, sharp as a razor and freezing cold, flew at her.

Saeko didn't have time to think. Her instincts took over. She spun, her katana meeting the crescent of shadow with a blast of her own wind. The two forces canceled each other out with a hiss.

The fight was on.

It was the hardest fight they had ever been in. The Sentinel didn't get tired. It didn't make mistakes. It was like fighting a mirror that could predict their moves. It used Alex's own fighting style against him—powerful, direct blows mixed with sudden, precise thrusts. Against Saeko, it used speed and tricky angles, firing blasts of shadow that moved like living things, trying to trap her.

They tried to fight it together, but the Sentinel was always one step ahead. When Alex tried to flank it, it would create a wall of white light to block him. When Saeko tried to attack from above, a dome of shadow would form over it. It was defending itself perfectly.

"We need to break the runes!" Alex shouted, blocking a double slash from both of the Sentinel's swords. "It's drawing power from them!"

Saeko nodded. She broke away from the fight, darting toward the edge of the room where the white runes glowed on the floor. She raised her katana, gathering wind for a powerful strike.

The Sentinel's blank face turned toward her. It pointed its shadow sword. The blue runes on the ceiling pulsed, and a rain of sharp, black icicles shot down at Saeko, forcing her to dive and roll away.

"It won't let us near them!" she yelled, cutting the last few icicles out of the air.

Alex gritted his teeth. They were strong, but they couldn't beat something with an endless power supply. They needed a new plan. He looked at the Sentinel, at the perfect split between light and shadow on its body.

An idea clicked.

"Saeko!" he called out. "Don't attack the runes! Attack it! But not together! We need to confuse it!"

He didn't explain more. He trusted her to understand.

He charged the Sentinel, not with his usual controlled style, but with pure, overwhelming aggression. He poured fire into his sword until it burned like a piece of the sun. He attacked not to win, but to demand every single bit of the Sentinel's attention.

The creature reacted. It met his fire with blazing white light, its form shifting to focus on him. It became brighter, more solid, its movements matching Alex's raw power.

This was what Alex wanted.

"Now, Saeko! The shadow side!" he roared, locking blades with the Sentinel, holding it in place.

Saeko saw it. While the Sentinel was focused on Alex, the glowing white half of its body was pulsing with energy. But the dark blue shadow half seemed slightly faded, less focused.

She didn't use a big, flashy attack. She used the fastest, most precise strike she knew. She became the wind. She shot across the room, a green and silver streak, and aimed her katana not at the Sentinel's core, but at the exact line where the white light met the blue shadow on its sword arm.

Her blade, sharpened by a whisper of focused wind, hit the dividing line.

There was a sound like a crystal glass cracking.

The Sentinel shuddered. The seamless blend of light and shadow broke. The shadow on its arm flickered, becoming unstable.

It was distracted for a split second. A split second was all Alex needed.

His heterochromia flashed—blue and silver for a heartbeat. He didn't stop time. He just bent it around his own sword. To the Sentinel, his next thrust seemed to come from three different angles at once.

It tried to block, but its shadow sword was wavering. Alex's real sword slipped through its guard.

He didn't aim for a kill shot. He aimed for the same dividing line, but on the Sentinel's chest.

His dark blade, carrying the weight of his returning temporal power, pierced the spot where light met dark.

The effect was instant.

The Sentinel froze. The white light and the blue shadow began to swirl violently around the point of Alex's sword, no longer in harmony. They started to pull apart from each other.

A low hum built in the room, rising to a painful whine.

"Get back!" Alex yelled, yanking his sword free and leaping toward Saeko.

They dove behind a slight rise in the black stone floor just as the Sentinel came apart.

There was no explosion. There was an implosion. The light and the shadow sucked inward, collapsing into a tiny, brilliant point of nothing. Then, with a final POP that hurt their ears, it vanished.

The white runes on the floor and the blue runes on the ceiling flickered and went dark, crumbling into dust.

Silence returned, deeper than before.

Slowly, Alex and Saeko got to their feet. The circular room was just a room now. On the far wall, a final portal had opened. This one didn't shimmer with dungeon magic. It glowed with a steady, warm, golden light. The exit.

They looked at each other. They were both bruised, tired, and covered in the strange, sparkling dust of the fallen Sentinel.

"We did it," Saeko said, the words feeling huge.

"We did," Alex agreed. He walked over to her.