The Demon king's Last oath

The air grew colder as Caius and the stranger approached the ruin, the sharp incline of the ridge forcing them to move slowly. The crumbling tower loomed above them, its jagged silhouette stark against the night sky. Vines twisted around its stone walls, and faint cracks glowed with an eerie blue light.

Caius dismounted at the base of the ridge, tying his horse to a low branch. The pull in his chest was stronger now, almost overwhelming, like a silent call urging him forward.

"This place feels… wrong," the stranger muttered, their silver eyes scanning the darkened landscape.

Caius glanced at them. "Afraid?"

The stranger grinned, though it didn't reach their eyes. "Cautious. Places like this tend to bite back."

"Then stay here," Caius said, his tone even.

The stranger scoffed, pulling their hood lower. "Not a chance, boy. I want to see what's so important that it dragged you all the way out here."

Caius didn't respond. Instead, he adjusted the strap of his satchel and began the climb, his boots crunching against loose rocks.

The closer they got to the ruin, the more the air seemed to change. It grew heavy, charged with an unnatural energy that prickled against their skin. The faint hum of magic pulsed through the ground, each step bringing them closer to its source.

Caius paused at the base of the tower, his sharp blue eyes studying the structure. The entrance was a gaping archway, its edges worn smooth by time. Faint symbols were etched into the stone, glowing faintly in the darkness.

"Old magic," the stranger murmured, their gaze fixed on the runes.

"You recognize it?" Caius asked.

The stranger nodded. "Binding runes. Meant to keep something in—or keep something out."

Caius stepped closer, his hand hovering near the stone. The glow of the runes brightened, and the air around him grew colder.

"Careful," the stranger warned.

"I can feel it," Caius said, his voice quiet. "There's something inside."

The stranger frowned. "And I'm guessing it doesn't want us there."

As if in answer, a low growl echoed from the darkness of the archway.

Caius tensed, his hand dropping to the dagger at his side. The stranger stepped back, their silver eyes scanning the shadows.

The growl grew louder, followed by the scrape of claws against stone. Then, from the darkness of the archway, a figure emerged.

It was a beast, its body twisted and unnatural. Its fur was matted and black as pitch, and its eyes burned with an otherworldly blue light. Two more creatures followed, their movements jerky and unnatural, like puppets pulled by invisible strings.

"Gatekeepers," the stranger said, their voice low. "They're bound to the runes."

Caius's jaw tightened. "Can we break the binding?"

The stranger shook their head. "Not without knowing the exact spell. And I doubt they'll give us the time to figure it out."

The lead creature snarled, its glowing eyes fixed on Caius. Then, with a sudden burst of speed, it charged.

Caius sidestepped the first strike, his dagger flashing as he slashed at the beast's side. The blade cut deep, but instead of blood, a dark, smoky substance oozed from the wound.

The creature didn't slow. It turned sharply, its claws swiping toward Caius's chest. He barely managed to block with his arm, the force of the blow sending him stumbling back.

The stranger moved swiftly, their glowing runes lighting up the dark. With a sharp motion, they flung a burst of silver energy at the second beast, striking it in the chest. The creature howled, its form flickering as the energy burned through it.

"These things don't go down easy," the stranger said, dodging another swipe.

Caius steadied himself, his blue eyes flickering with crimson. "Then we don't hold back."

He raised his hand, and dark flames erupted from his palm, coiling around his arm like a living thing. The lead creature hesitated, its glowing eyes narrowing as the fire flared brighter.

"You want a fight?" Caius said, his voice low. "Then come and get it."

The flames lashed out, striking the creature square in the chest. It howled as the fire consumed it, its body collapsing into ash.

The remaining two beasts hesitated, their movements jerky as if they were struggling against an unseen force.

"They're tied to the runes," the stranger said. "If we don't finish them, they'll just keep coming."

Caius nodded, his flames flickering as he focused on the second beast. The creature lunged, but Caius was faster. He stepped forward, the fire surging from his hand in a concentrated burst. The beast dissolved into smoke, its twisted form unraveling into the night.

The final creature snarled, its glowing eyes darting between Caius and the stranger. Then, with a guttural growl, it turned and fled into the darkness.

Caius lowered his hand, the flames flickering out as the air grew still once more. His chest heaved, his small frame trembling slightly from the effort.

The stranger approached, their silver eyes studying him carefully. "You've got some serious firepower, boy. But you're running on borrowed time."

Caius looked at them, his expression guarded. "What do you mean?"

"That power of yours," the stranger said, gesturing to his hand. "It's not normal. It's… unstable. If you're not careful, it'll burn you from the inside out."

Caius frowned, his jaw tightening. "I can handle it."

The stranger raised an eyebrow. "You sure about that?"

Before Caius could respond, the faint hum of magic pulsed through the air again. The runes on the archway began to glow brighter, the light flickering like a heartbeat.

"Looks like we woke something up," the stranger muttered.

Caius stepped toward the archway, his blue eyes narrowing. "Then let's find out what it is."

The pair entered the ruin cautiously, their footsteps echoing against the cold stone. The interior was dark, the walls etched with the same glowing runes that lined the entrance.

Caius felt the pull stronger than ever, a deep vibration that seemed to resonate with the very core of his being.

"This place…" he murmured.

"Feels alive," the stranger finished, their voice hushed.

At the center of the chamber, a pedestal stood bathed in faint blue light. On it rested an ancient object—a shard of black crystal, its surface pulsing with a dark energy.

Caius approached slowly, his gaze fixed on the shard. The pull in his chest was almost unbearable now, as though the shard were calling to him.

"What is it?" he asked, his voice barely above a whisper.

The stranger's expression darkened. "Trouble."