Disclaimer: I own nothing, all of this is written for the sole porpuse of my own and (other fans') amusement. It would certainly be nice to earn money with this but I don't.

Prologue

„Emrys, don't forget there is a price for everything."

Merlin stared out at the swirling lights over the lake's rippled surface. He was cowering on the ground, still desperately clutching Arthur's lifeless form to his chest. "I know. I'm prepared to give everything! You can have my life in exchange for his!" he yelled.

The lake's waters started rising, the Sidhe moving faster. A storm was coming.
"It's not your life we seek, warlock."

Merlin could feel the despair growing. The body in his arms was already cooling, life's breath having fled from it several minutes ago. He wiped away the tears in the corner of his eyes and tried to focus on the eerily glowing lights.
"Then please… tell me what you want!" He sounded chocked now. Anguish was closing off his throat, making his voice raw and barely able to contain the sobs that threatened escape. "I'd do anything…"

"It's not your life we seek, warlock. It's your soul…"

The wind picked up and carried the disembodied words over the shores of lake Avalon, over the hills and forests surrounding it, until they finally died away in the distance but still resonated within every fibre of Merlin's being.

"My soul? " he stammered, "but…"

"You said anything. Is the magnitude of your loyalty so limited to mortal scales that an immortal price puts you off?"

Merlin shook his head. The Sidhe were taunting him, their spiteful laughter resounding in the wind that violently blew through the leaves and tore at his clothes. He knew they were trying to lure him in and that this deal was something that he would most likely come to regret, but when he had said anything he had meant it. He didn't really know what his soul implied but that didn't matter because in the end Merlin would always pay the price. Arthur's life was worth it and getting him back was worth everything.

So he nodded and stared ahead into the madly dancing circus of lights hovering over the lake's turbulent surface. "You shall have my soul in exchange for King Arthur's life."
The Sidhe started hissing in triumph and laughter but Merlin held out his hand, his eyes glowing gold, "but only…" he took a deep breath, " but only if you promise to never threaten the king's or any of his associates' lives again and welcome him back to Avalon once natural causes take him."

The swirling light that must have been the Sidhe elder hovered in front of him before the grave resonance of his voice struck Merlin and made every living thing in their direct environment quiver.

"So it shall be then."

The lake's waters started swelling, lapping around Merlin's feet, slowly engulfing him and Arthur. Maybe this was a mistake after all, Merlin thought trembling while the storm and the Sidhe's excited voices raged over him. A cold, dark fear had taken hold of him. The deal he was making now was not about an elaborate healing spell to suck the dark poison of Mordred's cursed blade out of Arthur's body but cheating death. Nobody could bring back the dead though, that was what Lancelot's return had taught him.
By the time the rising waters reached Merlin's chest, his heart was beating so rapidly he could barely contain himself. He clutched Arthur's stiff body closer to his own while the merciless rain pounded down on them. What did it mean to surrender his soul to the Sidhe? He didn't mind dying, he didn't mind joining the ranks of Avalon in Arthur's stead but he had to make sure the resurrected king was more than a mere shade. He opened his mouth to ask but the Sidhe's voices – surprisingly clear over the storm – prevented him.

"Fear not, Emrys. We will uphold our end of the bargain. It is yourself you should be worried for."

That was the last thing he heard before the water had risen so high Merlin could no longer breathe. He was pulled under and Arthur slipped from his grip, getting lost in the murky darkness of the lake. Merlin wanted to scream, but only muted bubbles escaped his mouth while he tried to reach for his king. But Arthur was gone and Merlin tried to find him, his limbs flailing in panic, while the pressure in his lungs got harder and harder to bear. Without seeing he made wild grasps at nothing and was lost.

It became more and more silent underneath the surface and Merlin noticed that it was getting darker too. Though not the waters were so devoid of light, it was the one in his eyes that was slowly fading, rendering him blind. So he stopped moving, stopped searching and let himself glide soundlessly into the bottomless depths of lake Avalon.