Bone Mountain rose like a dead god's crown.
Its base was a fortress of jagged stone and old-world wreckage—collapsed satellite dishes, rusted antennas, shattered energy pylons buried in the cliffs like fossils. The peak glowed faintly red, and just beneath that cursed summit, carved into the heart of the rock, was the Vault: Sigil 7.
They stood at the final ridge, staring down at the entrance—a yawning archway shaped like a serpent's jaw, ringed with ancient runes still flickering faintly. Guards in heavy armor patrolled the perimeter, their weapons humming with shardlight, powered by what little magic the Ardent Choir could still siphon from the old grid.
"Too many to fight," Aeska whispered.
"We don't fight," Kairo said. "We slip past."
She glanced at him. "You're confident now."
"No," he replied. "Just desperate."
They waited until nightfall, cloaked in mist, then moved—silent, swift, shadows among the ash. Kairo had memorized the shifts in guard patterns, watching with the patience he'd learned surviving ruined cities and hunting beasts. With Aeska's direction and a few carefully timed shimmerdust charges, they passed the outer defenses.
But the deeper they went into the Vault, the stranger the air became.
The stone pulsed with warmth. The walls bore carvings—not of gods, but eyes. Hundreds of them. Watching. Bleeding.
And then they heard it.
A song.
Low, humming, echoing through the tunnels—not mechanical, not magical, but human. A voice filled with sorrow and steel.
Kairo froze.
It was Yui's voice.
Aeska grabbed his arm. "Don't rush—"
Too late.
He sprinted down the tunnel, following the voice, deeper and deeper, until the stone gave way to a massive chamber—vaulted, circular, filled with flickering red light and surrounded by floating mirrors.
At the center: Yui.
She hovered just above the floor, suspended in a web of crimson thread and rune-bound glass. Her eyes were closed, her lips moving as she sang the same line over and over in the old tongue:
"Through fire and ash, the world breaks thrice… and thrice must be born again…"
"YUI!" Kairo screamed.
She didn't answer.
But someone else did.
A figure stepped from the shadows behind the mirrors, tall and draped in robes of woven glass and black silk. His face was pale, almost translucent, and his eyes glowed gold behind a porcelain mask split down the center.
"Brother," the figure said, voice smooth as poison. "At last."
Kairo raised his spear.
"Who are you?"
The figure bowed.
"I am the one born from her memories. The pain she locked away. The rage she never spoke. I am what she needed when she was alone."
Aeska entered, dagger ready. "The Echo Prince."
He smiled.
"You say it like a curse. I wear it as a crown."
"You're not real," Kairo said, stepping closer. "You're just a shard-born hallucination. A parasite."
"Oh, but I am very real. I was born from the seal Yui broke when she first called out for you. When you didn't come."
Kairo faltered.
"She waited," the Echo Prince said. "Longer than any child should have. And when the Choir came to break her, I was all that kept her sane. Her shadow. Her shield. Her brother, when you weren't."
Kairo roared and lunged.
The Echo Prince caught the spear with one hand.
And shattered it.
Kairo stumbled back, stunned.
"You're not ready," the Prince said gently. "But I'll make you ready."
With a wave, the mirrors flared. One by one, they turned to show Kairo's memories—his failures. The burning village. The night he ran instead of fighting. The people he left behind.
Yui's voice echoed louder, her song strained now—cracking under pressure.
"You see?" the Echo Prince whispered. "You break everything you try to save."
"No," Kairo growled, fists clenched. "Not this time."
From his belt, he pulled the fox mask.
Slipped it on.
The world sharpened.
The mark on his wrist blazed like fire.
He stepped into the center of the mirrors, light flaring around him.
"I'm not the boy who ran," he said. "I'm the Ashborn. And I've come to take her back."
The Echo Prince's smile faded.
For the first time, he looked uncertain.