On the fourth day in the Gut, they found it. A faint, blue glow pulsed from the cracks in the cavern floor. Kaelen knelt down, touching the light. It wasn't fire. It felt like... a vibration.
"What is that?" Lyra asked, her glass-like eyes reflecting the azure hue.
"The blood of the world," a voice echoed. Master Vane was standing at the end of the tunnel, silhouetted by the exit's light. "This is Aetheria. The energy that the new kings use to build their cities. And the energy we use to hide in their shadows."
Vane held up a dagger made of black glass. As he touched the blue glow, the dagger began to hum. The blade didn't just look sharp; it looked like it could cut through reality itself.
"This world is changing, children," Vane said. "The old ways of bone and fur are dying. The age of the 'Civilized' is here, and they bring magic. If you cannot harness the Aetheria, you will be nothing but meat for their machines."
Kaelen felt a chill. This wasn't just the Middle Ages. This was a world on the brink of a magical industrial revolution. And he was being trained to be the ghost in that machine.